/* pngrtran.c - transforms the data in a row for PNG readers
 *
 * Last changed in libpng 1.4.2 [May 6, 2010]
 * Copyright (c) 1998-2010 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 *
 * This file contains functions optionally called by an application
 * in order to tell libpng how to handle data when reading a PNG.
 * Transformations that are used in both reading and writing are
 * in pngtrans.c.
 */

#include "png.h"
#define PNG_NO_PEDANTIC_WARNINGS
#ifdef PNG_READ_SUPPORTED
    #include "pngpriv.h"

/* Set the action on getting a CRC error for an ancillary or critical chunk. */
void PNGAPI
png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
{
    png_debug(1, "in png_set_crc_action");

    if (png_ptr == NULL)
        return;

    /* Tell libpng how we react to CRC errors in critical chunks */
    switch (crit_action)
    {
        case PNG_CRC_NO_CHANGE:                      /* Leave setting as is */
            break;

        case PNG_CRC_WARN_USE:                             /* Warn/use data */
            png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
            png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
            break;

        case PNG_CRC_QUIET_USE:                           /* Quiet/use data */
            png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
            png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
                              PNG_FLAG_CRC_CRITICAL_IGNORE;
            break;

        case PNG_CRC_WARN_DISCARD:  /* Not a valid action for critical data */
            png_warning(png_ptr,
                        "Can't discard critical data on CRC error");
        case PNG_CRC_ERROR_QUIT:                              /* Error/quit */

        case PNG_CRC_DEFAULT:
        default:
            png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
            break;
    }

    /* Tell libpng how we react to CRC errors in ancillary chunks */
    switch (ancil_action)
    {
        case PNG_CRC_NO_CHANGE:                     /* Leave setting as is */
            break;

        case PNG_CRC_WARN_USE:                            /* Warn/use data */
            png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
            png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
            break;

        case PNG_CRC_QUIET_USE:                          /* Quiet/use data */
            png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
            png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
                              PNG_FLAG_CRC_ANCILLARY_NOWARN;
            break;

        case PNG_CRC_ERROR_QUIT:                             /* Error/quit */
            png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
            png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
            break;

        case PNG_CRC_WARN_DISCARD:                    /* Warn/discard data */

        case PNG_CRC_DEFAULT:
        default:
            png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
            break;
    }
}

    #if defined (PNG_READ_BACKGROUND_SUPPORTED) && \
    defined (PNG_FLOATING_POINT_SUPPORTED)
/* Handle alpha and tRNS via a background color */
void PNGAPI
png_set_background(png_structp png_ptr,
                   png_color_16p background_color, int background_gamma_code,
                   int need_expand, double background_gamma)
{
    png_debug(1, "in png_set_background");

    if (png_ptr == NULL)
        return;
    if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
    {
        png_warning(png_ptr, "Application must supply a known background gamma");
        return;
    }

    png_ptr->transformations |= PNG_BACKGROUND;
    png_memcpy(&(png_ptr->background), background_color,
               png_sizeof(png_color_16));
    png_ptr->background_gamma = (float)background_gamma;
    png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
    png_ptr->transformations |= (need_expand ? PNG_BACKGROUND_EXPAND : 0);
}
    #endif

    #ifdef PNG_READ_16_TO_8_SUPPORTED
/* Strip 16 bit depth files to 8 bit depth */
void PNGAPI
png_set_strip_16(png_structp png_ptr)
{
    png_debug(1, "in png_set_strip_16");

    if (png_ptr == NULL)
        return;
    png_ptr->transformations |= PNG_16_TO_8;
}
    #endif

    #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
void PNGAPI
png_set_strip_alpha(png_structp png_ptr)
{
    png_debug(1, "in png_set_strip_alpha");

    if (png_ptr == NULL)
        return;
    png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
}
    #endif

    #ifdef PNG_READ_QUANTIZE_SUPPORTED
/* Quantize file to 8 bit.  Supply a palette, the current number
 * of elements in the palette, the maximum number of elements
 * allowed, and a histogram if possible.  If the current number
 * of colors is greater then the maximum number, the palette will be
 * modified to fit in the maximum number.  "full_quantize" indicates
 * whether we need a quantizeing cube set up for RGB images, or if we
 * simply are reducing the number of colors in a paletted image.
 */

typedef struct png_dsort_struct
{
    struct png_dsort_struct FAR* next;
    png_byte left;
    png_byte right;
} png_dsort;
typedef png_dsort FAR* png_dsortp;
typedef png_dsort FAR* FAR* png_dsortpp;

void PNGAPI
png_set_quantize(png_structp png_ptr, png_colorp palette,
                 int num_palette, int maximum_colors, png_uint_16p histogram,
                 int full_quantize)
{
    png_debug(1, "in png_set_quantize");

    if (png_ptr == NULL)
        return;
    png_ptr->transformations |= PNG_QUANTIZE;

    if (!full_quantize)
    {
        int i;

        png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
                                                        (png_uint_32)(num_palette * png_sizeof(png_byte)));
        for (i = 0; i < num_palette; i++)
            png_ptr->quantize_index[i] = (png_byte)i;
    }

    if (num_palette > maximum_colors)
    {
        if (histogram != NULL)
        {
            /* This is easy enough, just throw out the least used colors.
             * Perhaps not the best solution, but good enough.
             */

            int i;

            /* Initialize an array to sort colors */
            png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
                                                           (png_uint_32)(num_palette * png_sizeof(png_byte)));

            /* Initialize the quantize_sort array */
            for (i = 0; i < num_palette; i++)
                png_ptr->quantize_sort[i] = (png_byte)i;

            /* Find the least used palette entries by starting a
             * bubble sort, and running it until we have sorted
             * out enough colors.  Note that we don't care about
             * sorting all the colors, just finding which are
             * least used.
             */

            for (i = num_palette - 1; i >= maximum_colors; i--)
            {
                int done; /* To stop early if the list is pre-sorted */
                int j;

                done = 1;
                for (j = 0; j < i; j++)
                {
                    if (histogram[png_ptr->quantize_sort[j]]
                        < histogram[png_ptr->quantize_sort[j + 1]])
                    {
                        png_byte t;

                        t = png_ptr->quantize_sort[j];
                        png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
                        png_ptr->quantize_sort[j + 1] = t;
                        done = 0;
                    }
                }
                if (done)
                    break;
            }

            /* Swap the palette around, and set up a table, if necessary */
            if (full_quantize)
            {
                int j = num_palette;

                /* Put all the useful colors within the max, but don't
                 * move the others.
                 */
                for (i = 0; i < maximum_colors; i++)
                {
                    if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
                    {
                        do
                            j--;
                        while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
                        palette[i] = palette[j];
                    }
                }
            }
            else
            {
                int j = num_palette;

                /* Move all the used colors inside the max limit, and
                 * develop a translation table.
                 */
                for (i = 0; i < maximum_colors; i++)
                {
                    /* Only move the colors we need to */
                    if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
                    {
                        png_color tmp_color;

                        do
                            j--;
                        while ((int)png_ptr->quantize_sort[j] >= maximum_colors);

                        tmp_color = palette[j];
                        palette[j] = palette[i];
                        palette[i] = tmp_color;
                        /* Indicate where the color went */
                        png_ptr->quantize_index[j] = (png_byte)i;
                        png_ptr->quantize_index[i] = (png_byte)j;
                    }
                }

                /* Find closest color for those colors we are not using */
                for (i = 0; i < num_palette; i++)
                {
                    if ((int)png_ptr->quantize_index[i] >= maximum_colors)
                    {
                        int min_d, k, min_k, d_index;

                        /* Find the closest color to one we threw out */
                        d_index = png_ptr->quantize_index[i];
                        min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
                        for (k = 1, min_k = 0; k < maximum_colors; k++)
                        {
                            int d;

                            d = PNG_COLOR_DIST(palette[d_index], palette[k]);

                            if (d < min_d)
                            {
                                min_d = d;
                                min_k = k;
                            }
                        }
                        /* Point to closest color */
                        png_ptr->quantize_index[i] = (png_byte)min_k;
                    }
                }
            }
            png_free(png_ptr, png_ptr->quantize_sort);
            png_ptr->quantize_sort = NULL;
        }
        else
        {
            /* This is much harder to do simply (and quickly).  Perhaps
             * we need to go through a median cut routine, but those
             * don't always behave themselves with only a few colors
             * as input.  So we will just find the closest two colors,
             * and throw out one of them (chosen somewhat randomly).
             * [We don't understand this at all, so if someone wants to
             *  work on improving it, be our guest - AED, GRP]
             */
            int i;
            int max_d;
            int num_new_palette;
            png_dsortp t;
            png_dsortpp hash;

            t = NULL;

            /* Initialize palette index arrays */
            png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
                                                              (png_uint_32)(num_palette * png_sizeof(png_byte)));
            png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
                                                              (png_uint_32)(num_palette * png_sizeof(png_byte)));

            /* Initialize the sort array */
            for (i = 0; i < num_palette; i++)
            {
                png_ptr->index_to_palette[i] = (png_byte)i;
                png_ptr->palette_to_index[i] = (png_byte)i;
            }

            hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
                                                                  png_sizeof(png_dsortp)));

            num_new_palette = num_palette;

            /* Initial wild guess at how far apart the farthest pixel
             * pair we will be eliminating will be.  Larger
             * numbers mean more areas will be allocated, Smaller
             * numbers run the risk of not saving enough data, and
             * having to do this all over again.
             *
             * I have not done extensive checking on this number.
             */
            max_d = 96;

            while (num_new_palette > maximum_colors)
            {
                for (i = 0; i < num_new_palette - 1; i++)
                {
                    int j;

                    for (j = i + 1; j < num_new_palette; j++)
                    {
                        int d;

                        d = PNG_COLOR_DIST(palette[i], palette[j]);

                        if (d <= max_d)
                        {

                            t = (png_dsortp)png_malloc_warn(png_ptr,
                                                            (png_uint_32)(png_sizeof(png_dsort)));
                            if (t == NULL)
                                break;
                            t->next = hash[d];
                            t->left = (png_byte)i;
                            t->right = (png_byte)j;
                            hash[d] = t;
                        }
                    }
                    if (t == NULL)
                        break;
                }

                if (t != NULL)
                    for (i = 0; i <= max_d; i++)
                    {
                        if (hash[i] != NULL)
                        {
                            png_dsortp p;

                            for (p = hash[i]; p; p = p->next)
                            {
                                if ((int)png_ptr->index_to_palette[p->left]
                                    < num_new_palette &&
                                    (int)png_ptr->index_to_palette[p->right]
                                    < num_new_palette)
                                {
                                    int j, next_j;

                                    if (num_new_palette & 0x01)
                                    {
                                        j = p->left;
                                        next_j = p->right;
                                    }
                                    else
                                    {
                                        j = p->right;
                                        next_j = p->left;
                                    }

                                    num_new_palette--;
                                    palette[png_ptr->index_to_palette[j]]
                                        = palette[num_new_palette];
                                    if (!full_quantize)
                                    {
                                        int k;

                                        for (k = 0; k < num_palette; k++)
                                        {
                                            if (png_ptr->quantize_index[k] ==
                                                png_ptr->index_to_palette[j])
                                                png_ptr->quantize_index[k] =
                                                    png_ptr->index_to_palette[next_j];
                                            if ((int)png_ptr->quantize_index[k] ==
                                                num_new_palette)
                                                png_ptr->quantize_index[k] =
                                                    png_ptr->index_to_palette[j];
                                        }
                                    }

                                    png_ptr->index_to_palette[png_ptr->palette_to_index
                                                              [num_new_palette]] = png_ptr->index_to_palette[j];
                                    png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
                                        = png_ptr->palette_to_index[num_new_palette];

                                    png_ptr->index_to_palette[j] =
                                        (png_byte)num_new_palette;
                                    png_ptr->palette_to_index[num_new_palette] =
                                        (png_byte)j;
                                }
                                if (num_new_palette <= maximum_colors)
                                    break;
                            }
                            if (num_new_palette <= maximum_colors)
                                break;
                        }
                    }

                for (i = 0; i < 769; i++)
                {
                    if (hash[i] != NULL)
                    {
                        png_dsortp p = hash[i];
                        while (p)
                        {
                            t = p->next;
                            png_free(png_ptr, p);
                            p = t;
                        }
                    }
                    hash[i] = 0;
                }
                max_d += 96;
            }
            png_free(png_ptr, hash);
            png_free(png_ptr, png_ptr->palette_to_index);
            png_free(png_ptr, png_ptr->index_to_palette);
            png_ptr->palette_to_index = NULL;
            png_ptr->index_to_palette = NULL;
        }
        num_palette = maximum_colors;
    }
    if (png_ptr->palette == NULL)
    {
        png_ptr->palette = palette;
    }
    png_ptr->num_palette = (png_uint_16)num_palette;

    if (full_quantize)
    {
        int i;
        png_bytep distance;
        int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
                         PNG_QUANTIZE_BLUE_BITS;
        int num_red = (1 << PNG_QUANTIZE_RED_BITS);
        int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
        int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
        png_size_t num_entries = ((png_size_t)1 << total_bits);

        png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
                                                        (png_uint_32)(num_entries * png_sizeof(png_byte)));

        distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
                                                                png_sizeof(png_byte)));
        png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));

        for (i = 0; i < num_palette; i++)
        {
            int ir, ig, ib;
            int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
            int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
            int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));

            for (ir = 0; ir < num_red; ir++)
            {
                /* int dr = abs(ir - r); */
                int dr = ((ir > r) ? ir - r : r - ir);
                int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
                                      PNG_QUANTIZE_GREEN_BITS));

                for (ig = 0; ig < num_green; ig++)
                {
                    /* int dg = abs(ig - g); */
                    int dg = ((ig > g) ? ig - g : g - ig);
                    int dt = dr + dg;
                    int dm = ((dr > dg) ? dr : dg);
                    int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);

                    for (ib = 0; ib < num_blue; ib++)
                    {
                        int d_index = index_g | ib;
                        /* int db = abs(ib - b); */
                        int db = ((ib > b) ? ib - b : b - ib);
                        int dmax = ((dm > db) ? dm : db);
                        int d = dmax + dt + db;

                        if (d < (int)distance[d_index])
                        {
                            distance[d_index] = (png_byte)d;
                            png_ptr->palette_lookup[d_index] = (png_byte)i;
                        }
                    }
                }
            }
        }

        png_free(png_ptr, distance);
    }
}
    #endif /* PNG_READ_QUANTIZE_SUPPORTED */

    #if defined (PNG_READ_GAMMA_SUPPORTED) && defined (PNG_FLOATING_POINT_SUPPORTED)
/* Transform the image from the file_gamma to the screen_gamma.  We
 * only do transformations on images where the file_gamma and screen_gamma
 * are not close reciprocals, otherwise it slows things down slightly, and
 * also needlessly introduces small errors.
 *
 * We will turn off gamma transformation later if no semitransparent entries
 * are present in the tRNS array for palette images.  We can't do it here
 * because we don't necessarily have the tRNS chunk yet.
 */
void PNGAPI
png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
{
    png_debug(1, "in png_set_gamma");

    if (png_ptr == NULL)
        return;

    if ((fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD) ||
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
        (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
        png_ptr->transformations |= PNG_GAMMA;
    png_ptr->gamma = (float)file_gamma;
    png_ptr->screen_gamma = (float)scrn_gamma;
}
    #endif

    #ifdef PNG_READ_EXPAND_SUPPORTED
/* Expand paletted images to RGB, expand grayscale images of
 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
 * to alpha channels.
 */
void PNGAPI
png_set_expand(png_structp png_ptr)
{
    png_debug(1, "in png_set_expand");

    if (png_ptr == NULL)
        return;

    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}

/* GRR 19990627:  the following three functions currently are identical
 *  to png_set_expand().  However, it is entirely reasonable that someone
 *  might wish to expand an indexed image to RGB but *not* expand a single,
 *  fully transparent palette entry to a full alpha channel--perhaps instead
 *  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
 *  the transparent color with a particular RGB value, or drop tRNS entirely.
 *  IOW, a future version of the library may make the transformations flag
 *  a bit more fine-grained, with separate bits for each of these three
 *  functions.
 *
 *  More to the point, these functions make it obvious what libpng will be
 *  doing, whereas "expand" can (and does) mean any number of things.
 *
 *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
 *  to expand only the sample depth but not to expand the tRNS to alpha
 *  and its name was changed to png_set_expand_gray_1_2_4_to_8().
 */

/* Expand paletted images to RGB. */
void PNGAPI
png_set_palette_to_rgb(png_structp png_ptr)
{
    png_debug(1, "in png_set_palette_to_rgb");

    if (png_ptr == NULL)
        return;

    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}

/* Expand grayscale images of less than 8-bit depth to 8 bits. */
void PNGAPI
png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
{
    png_debug(1, "in png_set_expand_gray_1_2_4_to_8");

    if (png_ptr == NULL)
        return;

    png_ptr->transformations |= PNG_EXPAND;
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}



/* Expand tRNS chunks to alpha channels. */
void PNGAPI
png_set_tRNS_to_alpha(png_structp png_ptr)
{
    png_debug(1, "in png_set_tRNS_to_alpha");

    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
    #endif /* defined(PNG_READ_EXPAND_SUPPORTED) */

    #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
void PNGAPI
png_set_gray_to_rgb(png_structp png_ptr)
{
    png_debug(1, "in png_set_gray_to_rgb");

    png_ptr->transformations |= PNG_GRAY_TO_RGB;
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
    #endif

    #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
        #ifdef PNG_FLOATING_POINT_SUPPORTED
/* Convert a RGB image to a grayscale of the same width.  This allows us,
 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
 */

void PNGAPI
png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
                    double green)
{
    int red_fixed = (int)((float)red * 100000.0 + 0.5);
    int green_fixed = (int)((float)green * 100000.0 + 0.5);
    if (png_ptr == NULL)
        return;
    png_set_rgb_to_gray_fixed(png_ptr, error_action, red_fixed, green_fixed);
}
        #endif

void PNGAPI
png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
                          png_fixed_point red, png_fixed_point green)
{
    png_debug(1, "in png_set_rgb_to_gray");

    if (png_ptr == NULL)
        return;

    switch (error_action)
    {
        case 1: png_ptr->transformations |= PNG_RGB_TO_GRAY;
            break;

        case 2: png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
            break;

        case 3: png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
    }
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
    #ifdef PNG_READ_EXPAND_SUPPORTED
        png_ptr->transformations |= PNG_EXPAND;
    #else
    {
        png_warning(png_ptr,
                    "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
        png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
    }
    #endif
    {
        png_uint_16 red_int, green_int;
        if (red < 0 || green < 0)
        {
            red_int = 6968; /* .212671 * 32768 + .5 */
            green_int = 23434; /* .715160 * 32768 + .5 */
        }
        else if (red + green < 100000L)
        {
            red_int = (png_uint_16)(((png_uint_32)red * 32768L) / 100000L);
            green_int = (png_uint_16)(((png_uint_32)green * 32768L) / 100000L);
        }
        else
        {
            png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
            red_int = 6968;
            green_int = 23434;
        }
        png_ptr->rgb_to_gray_red_coeff = red_int;
        png_ptr->rgb_to_gray_green_coeff = green_int;
        png_ptr->rgb_to_gray_blue_coeff =
            (png_uint_16)(32768 - red_int - green_int);
    }
}
    #endif

    #if defined (PNG_READ_USER_TRANSFORM_SUPPORTED) || \
    defined (PNG_WRITE_USER_TRANSFORM_SUPPORTED)
void PNGAPI
png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
                               read_user_transform_fn)
{
    png_debug(1, "in png_set_read_user_transform_fn");

    if (png_ptr == NULL)
        return;

    #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    png_ptr->transformations |= PNG_USER_TRANSFORM;
    png_ptr->read_user_transform_fn = read_user_transform_fn;
    #endif
}
    #endif

/* Initialize everything needed for the read.  This includes modifying
 * the palette.
 */
void /* PRIVATE */
png_init_read_transformations(png_structp png_ptr)
{
    png_debug(1, "in png_init_read_transformations");

    {
        #if defined (PNG_READ_BACKGROUND_SUPPORTED) || \
        defined (PNG_READ_SHIFT_SUPPORTED) || \
        defined (PNG_READ_GAMMA_SUPPORTED)
        int color_type = png_ptr->color_type;
        #endif

        #if defined (PNG_READ_EXPAND_SUPPORTED) && defined (PNG_READ_BACKGROUND_SUPPORTED)

        #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
        /* Detect gray background and attempt to enable optimization
         * for gray --> RGB case
         *
         * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
         * RGB_ALPHA (in which case need_expand is superfluous anyway), the
         * background color might actually be gray yet not be flagged as such.
         * This is not a problem for the current code, which uses
         * PNG_BACKGROUND_IS_GRAY only to decide when to do the
         * png_do_gray_to_rgb() transformation.
         */
        if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
            !(color_type & PNG_COLOR_MASK_COLOR))
        {
            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
        }
        else if ((png_ptr->transformations & PNG_BACKGROUND) &&
                 !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
                 (png_ptr->transformations & PNG_GRAY_TO_RGB) &&
                 png_ptr->background.red == png_ptr->background.green &&
                 png_ptr->background.red == png_ptr->background.blue)
        {
            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
            png_ptr->background.gray = png_ptr->background.red;
        }
        #endif

        if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
            (png_ptr->transformations & PNG_EXPAND))
        {
            if (!(color_type & PNG_COLOR_MASK_COLOR)) /* i.e., GRAY or GRAY_ALPHA */
            {
                /* Expand background and tRNS chunks */
                switch (png_ptr->bit_depth)
                {
                    case 1:
                        png_ptr->background.gray *= (png_uint_16)0xff;
                        png_ptr->background.red = png_ptr->background.green
                                                      = png_ptr->background.blue = png_ptr->background.gray;
                        if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
                        {
                            png_ptr->trans_color.gray *= (png_uint_16)0xff;
                            png_ptr->trans_color.red = png_ptr->trans_color.green
                                                           = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
                        }
                        break;

                    case 2:
                        png_ptr->background.gray *= (png_uint_16)0x55;
                        png_ptr->background.red = png_ptr->background.green
                                                      = png_ptr->background.blue = png_ptr->background.gray;
                        if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
                        {
                            png_ptr->trans_color.gray *= (png_uint_16)0x55;
                            png_ptr->trans_color.red = png_ptr->trans_color.green
                                                           = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
                        }
                        break;

                    case 4:
                        png_ptr->background.gray *= (png_uint_16)0x11;
                        png_ptr->background.red = png_ptr->background.green
                                                      = png_ptr->background.blue = png_ptr->background.gray;
                        if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
                        {
                            png_ptr->trans_color.gray *= (png_uint_16)0x11;
                            png_ptr->trans_color.red = png_ptr->trans_color.green
                                                           = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
                        }
                        break;

                    case 8:

                    case 16:
                        png_ptr->background.red = png_ptr->background.green
                                                      = png_ptr->background.blue = png_ptr->background.gray;
                        break;
                }
            }
            else if (color_type == PNG_COLOR_TYPE_PALETTE)
            {
                png_ptr->background.red =
                    png_ptr->palette[png_ptr->background.index].red;
                png_ptr->background.green =
                    png_ptr->palette[png_ptr->background.index].green;
                png_ptr->background.blue =
                    png_ptr->palette[png_ptr->background.index].blue;

                #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
                if (png_ptr->transformations & PNG_INVERT_ALPHA)
                {
                    #ifdef PNG_READ_EXPAND_SUPPORTED
                    if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
                    #endif
                    {
                        /* Invert the alpha channel (in tRNS) unless the pixels are
                         * going to be expanded, in which case leave it for later
                         */
                        int i, istop;
                        istop = (int)png_ptr->num_trans;
                        for (i = 0; i < istop; i++)
                            png_ptr->trans_alpha[i] = (png_byte)(255 - png_ptr->trans_alpha[i]);
                    }
                }
                #endif

            }
        }
        #endif

        #if defined (PNG_READ_BACKGROUND_SUPPORTED) && defined (PNG_READ_GAMMA_SUPPORTED)
        png_ptr->background_1 = png_ptr->background;
        #endif
        #if defined (PNG_READ_GAMMA_SUPPORTED) && defined (PNG_FLOATING_POINT_SUPPORTED)

        if ((color_type == PNG_COLOR_TYPE_PALETTE && png_ptr->num_trans != 0)
            && (fabs(png_ptr->screen_gamma * png_ptr->gamma - 1.0)
                < PNG_GAMMA_THRESHOLD))
        {
            int i, k;
            k = 0;
            for (i = 0; i < png_ptr->num_trans; i++)
            {
                if (png_ptr->trans_alpha[i] != 0 && png_ptr->trans_alpha[i] != 0xff)
                    k = 1; /* Partial transparency is present */
            }
            if (k == 0)
                png_ptr->transformations &= ~PNG_GAMMA;
        }

        if ((png_ptr->transformations & (PNG_GAMMA | PNG_RGB_TO_GRAY)) &&
            png_ptr->gamma != 0.0)
        {
            png_build_gamma_table(png_ptr, png_ptr->bit_depth);

            #ifdef PNG_READ_BACKGROUND_SUPPORTED
            if (png_ptr->transformations & PNG_BACKGROUND)
            {
                if (color_type == PNG_COLOR_TYPE_PALETTE)
                {
                    /* Could skip if no transparency */
                    png_color back, back_1;
                    png_colorp palette = png_ptr->palette;
                    int num_palette = png_ptr->num_palette;
                    int i;
                    if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
                    {
                        back.red = png_ptr->gamma_table[png_ptr->background.red];
                        back.green = png_ptr->gamma_table[png_ptr->background.green];
                        back.blue = png_ptr->gamma_table[png_ptr->background.blue];

                        back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
                        back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
                        back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
                    }
                    else
                    {
                        double g, gs;

                        switch (png_ptr->background_gamma_type)
                        {
                            case PNG_BACKGROUND_GAMMA_SCREEN:
                                g = (png_ptr->screen_gamma);
                                gs = 1.0;
                                break;

                            case PNG_BACKGROUND_GAMMA_FILE:
                                g = 1.0 / (png_ptr->gamma);
                                gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                                break;

                            case PNG_BACKGROUND_GAMMA_UNIQUE:
                                g = 1.0 / (png_ptr->background_gamma);
                                gs = 1.0 / (png_ptr->background_gamma *
                                            png_ptr->screen_gamma);
                                break;
                            default:
                                g = 1.0; /* back_1 */
                                gs = 1.0; /* back */
                        }

                        if (fabs(gs - 1.0) < PNG_GAMMA_THRESHOLD)
                        {
                            back.red = (png_byte)png_ptr->background.red;
                            back.green = (png_byte)png_ptr->background.green;
                            back.blue = (png_byte)png_ptr->background.blue;
                        }
                        else
                        {
                            back.red = (png_byte)(pow(
                                                      (double)png_ptr->background.red / 255.0, gs) * 255.0 + .5);
                            back.green = (png_byte)(pow(
                                                        (double)png_ptr->background.green / 255.0, gs) * 255.0
                                                    + .5);
                            back.blue = (png_byte)(pow(
                                                       (double)png_ptr->background.blue / 255.0, gs) * 255.0 + .5);
                        }

                        back_1.red = (png_byte)(pow(
                                                    (double)png_ptr->background.red / 255.0, g) * 255.0 + .5);
                        back_1.green = (png_byte)(pow(
                                                      (double)png_ptr->background.green / 255.0, g) * 255.0 + .5);
                        back_1.blue = (png_byte)(pow(
                                                     (double)png_ptr->background.blue / 255.0, g) * 255.0 + .5);
                    }
                    for (i = 0; i < num_palette; i++)
                    {
                        if (i < (int)png_ptr->num_trans && png_ptr->trans_alpha[i] != 0xff)
                        {
                            if (png_ptr->trans_alpha[i] == 0)
                            {
                                palette[i] = back;
                            }
                            else /* if (png_ptr->trans_alpha[i] != 0xff) */
                            {
                                png_byte v, w;

                                v = png_ptr->gamma_to_1[palette[i].red];
                                png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
                                palette[i].red = png_ptr->gamma_from_1[w];

                                v = png_ptr->gamma_to_1[palette[i].green];
                                png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
                                palette[i].green = png_ptr->gamma_from_1[w];

                                v = png_ptr->gamma_to_1[palette[i].blue];
                                png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
                                palette[i].blue = png_ptr->gamma_from_1[w];
                            }
                        }
                        else
                        {
                            palette[i].red = png_ptr->gamma_table[palette[i].red];
                            palette[i].green = png_ptr->gamma_table[palette[i].green];
                            palette[i].blue = png_ptr->gamma_table[palette[i].blue];
                        }
                    }
                    /* Prevent the transformations being done again, and make sure
                     * that the now spurious alpha channel is stripped - the code
                     * has just reduced background composition and gamma correction
                     * to a simple alpha channel strip.
                     */
                    png_ptr->transformations &= ~PNG_BACKGROUND;
                    png_ptr->transformations &= ~PNG_GAMMA;
                    png_ptr->transformations |= PNG_STRIP_ALPHA;
                }
                /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
                else
                /* color_type != PNG_COLOR_TYPE_PALETTE */
                {
                    double m = (double)(((png_uint_32)1 << png_ptr->bit_depth) - 1);
                    double g = 1.0;
                    double gs = 1.0;

                    switch (png_ptr->background_gamma_type)
                    {
                        case PNG_BACKGROUND_GAMMA_SCREEN:
                            g = (png_ptr->screen_gamma);
                            gs = 1.0;
                            break;

                        case PNG_BACKGROUND_GAMMA_FILE:
                            g = 1.0 / (png_ptr->gamma);
                            gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                            break;

                        case PNG_BACKGROUND_GAMMA_UNIQUE:
                            g = 1.0 / (png_ptr->background_gamma);
                            gs = 1.0 / (png_ptr->background_gamma *
                                        png_ptr->screen_gamma);
                            break;
                    }

                    png_ptr->background_1.gray = (png_uint_16)(pow(
                                                                   (double)png_ptr->background.gray / m, g) * m + .5);
                    png_ptr->background.gray = (png_uint_16)(pow(
                                                                 (double)png_ptr->background.gray / m, gs) * m + .5);

                    if ((png_ptr->background.red != png_ptr->background.green) ||
                        (png_ptr->background.red != png_ptr->background.blue) ||
                        (png_ptr->background.red != png_ptr->background.gray))
                    {
                        /* RGB or RGBA with color background */
                        png_ptr->background_1.red = (png_uint_16)(pow(
                                                                      (double)png_ptr->background.red / m, g) * m + .5);
                        png_ptr->background_1.green = (png_uint_16)(pow(
                                                                        (double)png_ptr->background.green / m, g) * m + .5);
                        png_ptr->background_1.blue = (png_uint_16)(pow(
                                                                       (double)png_ptr->background.blue / m, g) * m + .5);
                        png_ptr->background.red = (png_uint_16)(pow(
                                                                    (double)png_ptr->background.red / m, gs) * m + .5);
                        png_ptr->background.green = (png_uint_16)(pow(
                                                                      (double)png_ptr->background.green / m, gs) * m + .5);
                        png_ptr->background.blue = (png_uint_16)(pow(
                                                                     (double)png_ptr->background.blue / m, gs) * m + .5);
                    }
                    else
                    {
                        /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
                        png_ptr->background_1.red = png_ptr->background_1.green
                                                        = png_ptr->background_1.blue = png_ptr->background_1.gray;
                        png_ptr->background.red = png_ptr->background.green
                                                      = png_ptr->background.blue = png_ptr->background.gray;
                    }
                }
            }
            else
            /* Transformation does not include PNG_BACKGROUND */
            #endif /* PNG_READ_BACKGROUND_SUPPORTED */
            if (color_type == PNG_COLOR_TYPE_PALETTE)
            {
                png_colorp palette = png_ptr->palette;
                int num_palette = png_ptr->num_palette;
                int i;

                for (i = 0; i < num_palette; i++)
                {
                    palette[i].red = png_ptr->gamma_table[palette[i].red];
                    palette[i].green = png_ptr->gamma_table[palette[i].green];
                    palette[i].blue = png_ptr->gamma_table[palette[i].blue];
                }

                /* Done the gamma correction. */
                png_ptr->transformations &= ~PNG_GAMMA;
            }
        }
        #ifdef PNG_READ_BACKGROUND_SUPPORTED
        else
        #endif
        #endif /* PNG_READ_GAMMA_SUPPORTED && PNG_FLOATING_POINT_SUPPORTED */
        #ifdef PNG_READ_BACKGROUND_SUPPORTED
        /* No GAMMA transformation */
        if ((png_ptr->transformations & PNG_BACKGROUND) &&
            (color_type == PNG_COLOR_TYPE_PALETTE))
        {
            int i;
            int istop = (int)png_ptr->num_trans;
            png_color back;
            png_colorp palette = png_ptr->palette;

            back.red = (png_byte)png_ptr->background.red;
            back.green = (png_byte)png_ptr->background.green;
            back.blue = (png_byte)png_ptr->background.blue;

            for (i = 0; i < istop; i++)
            {
                if (png_ptr->trans_alpha[i] == 0)
                {
                    palette[i] = back;
                }
                else if (png_ptr->trans_alpha[i] != 0xff)
                {
                    /* The png_composite() macro is defined in png.h */
                    png_composite(palette[i].red, palette[i].red,
                                  png_ptr->trans_alpha[i], back.red);
                    png_composite(palette[i].green, palette[i].green,
                                  png_ptr->trans_alpha[i], back.green);
                    png_composite(palette[i].blue, palette[i].blue,
                                  png_ptr->trans_alpha[i], back.blue);
                }
            }

            /* Handled alpha, still need to strip the channel. */
            png_ptr->transformations &= ~PNG_BACKGROUND;
            png_ptr->transformations |= PNG_STRIP_ALPHA;
        }
        #endif /* PNG_READ_BACKGROUND_SUPPORTED */

        #ifdef PNG_READ_SHIFT_SUPPORTED
        if ((png_ptr->transformations & PNG_SHIFT) &&
            (color_type == PNG_COLOR_TYPE_PALETTE))
        {
            png_uint_16 i;
            png_uint_16 istop = png_ptr->num_palette;
            int sr = 8 - png_ptr->sig_bit.red;
            int sg = 8 - png_ptr->sig_bit.green;
            int sb = 8 - png_ptr->sig_bit.blue;

            if (sr < 0 || sr > 8)
                sr = 0;
            if (sg < 0 || sg > 8)
                sg = 0;
            if (sb < 0 || sb > 8)
                sb = 0;
            for (i = 0; i < istop; i++)
            {
                png_ptr->palette[i].red >>= sr;
                png_ptr->palette[i].green >>= sg;
                png_ptr->palette[i].blue >>= sb;
            }
        }
        #endif /* PNG_READ_SHIFT_SUPPORTED */
    }
    #if !defined (PNG_READ_GAMMA_SUPPORTED) && !defined (PNG_READ_SHIFT_SUPPORTED) \
    && !defined (PNG_READ_BACKGROUND_SUPPORTED)
    if (png_ptr)
        return;
    #endif
}

/* Modify the info structure to reflect the transformations.  The
 * info should be updated so a PNG file could be written with it,
 * assuming the transformations result in valid PNG data.
 */
void /* PRIVATE */
png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
{
    png_debug(1, "in png_read_transform_info");

    #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
        if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
        {
            if (png_ptr->num_trans &&
                (png_ptr->transformations & PNG_EXPAND_tRNS))
                info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
            else
                info_ptr->color_type = PNG_COLOR_TYPE_RGB;
            info_ptr->bit_depth = 8;
            info_ptr->num_trans = 0;
        }
        else
        {
            if (png_ptr->num_trans)
            {
                if (png_ptr->transformations & PNG_EXPAND_tRNS)
                    info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
            }
            if (info_ptr->bit_depth < 8)
                info_ptr->bit_depth = 8;
            info_ptr->num_trans = 0;
        }
    }
    #endif

    #ifdef PNG_READ_BACKGROUND_SUPPORTED
    if (png_ptr->transformations & PNG_BACKGROUND)
    {
        info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
        info_ptr->num_trans = 0;
        info_ptr->background = png_ptr->background;
    }
    #endif

    #ifdef PNG_READ_GAMMA_SUPPORTED
    if (png_ptr->transformations & PNG_GAMMA)
    {
        #ifdef PNG_FLOATING_POINT_SUPPORTED
        info_ptr->gamma = png_ptr->gamma;
        #endif
        #ifdef PNG_FIXED_POINT_SUPPORTED
        info_ptr->int_gamma = png_ptr->int_gamma;
        #endif
    }
    #endif

    #ifdef PNG_READ_16_TO_8_SUPPORTED
    if ((png_ptr->transformations & PNG_16_TO_8) && (info_ptr->bit_depth == 16))
        info_ptr->bit_depth = 8;
    #endif

    #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    if (png_ptr->transformations & PNG_GRAY_TO_RGB)
        info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
    #endif

    #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
        info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
    #endif

    #ifdef PNG_READ_QUANTIZE_SUPPORTED
    if (png_ptr->transformations & PNG_QUANTIZE)
    {
        if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
             (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
            png_ptr->palette_lookup && info_ptr->bit_depth == 8)
        {
            info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
        }
    }
    #endif

    #ifdef PNG_READ_PACK_SUPPORTED
    if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
        info_ptr->bit_depth = 8;
    #endif

    if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
        info_ptr->channels = 1;
    else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
        info_ptr->channels = 3;
    else
        info_ptr->channels = 1;

    #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
        info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
    #endif

    if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
        info_ptr->channels++;

    #ifdef PNG_READ_FILLER_SUPPORTED
    /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
    if ((png_ptr->transformations & PNG_FILLER) &&
        ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
         (info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
    {
        info_ptr->channels++;
        /* If adding a true alpha channel not just filler */
        if (png_ptr->transformations & PNG_ADD_ALPHA)
            info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
    }
    #endif

    #if defined (PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
    defined (PNG_READ_USER_TRANSFORM_SUPPORTED)
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
    {
        if (info_ptr->bit_depth < png_ptr->user_transform_depth)
            info_ptr->bit_depth = png_ptr->user_transform_depth;
        if (info_ptr->channels < png_ptr->user_transform_channels)
            info_ptr->channels = png_ptr->user_transform_channels;
    }
    #endif

    info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
                                       info_ptr->bit_depth);

    info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);

    #ifndef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr)
        return;
    #endif
}

/* Transform the row.  The order of transformations is significant,
 * and is very touchy.  If you add a transformation, take care to
 * decide how it fits in with the other transformations here.
 */
void /* PRIVATE */
png_do_read_transformations(png_structp png_ptr)
{
    png_debug(1, "in png_do_read_transformations");

    if (png_ptr->row_buf == NULL)
    {
        #ifdef PNG_STDIO_SUPPORTED
        char msg[50];

        png_snprintf2(msg, 50,
                      "NULL row buffer for row %ld, pass %d", (long)png_ptr->row_number,
                      png_ptr->pass);
        png_error(png_ptr, msg);
        #else
        png_error(png_ptr, "NULL row buffer");
        #endif
    }
    #ifdef PNG_WARN_UNINITIALIZED_ROW
    if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
    /* Application has failed to call either png_read_start_image()
     * or png_read_update_info() after setting transforms that expand
     * pixels.  This check added to libpng-1.2.19
     */
    #if (PNG_WARN_UNINITIALIZED_ROW == 1)
        png_error(png_ptr, "Uninitialized row");
    #else
        png_warning(png_ptr, "Uninitialized row");
    #endif
    #endif

    #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
        if (png_ptr->row_info.color_type == PNG_COLOR_TYPE_PALETTE)
        {
            png_do_expand_palette(&(png_ptr->row_info), png_ptr->row_buf + 1,
                                  png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
        }
        else
        {
            if (png_ptr->num_trans &&
                (png_ptr->transformations & PNG_EXPAND_tRNS))
                png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
                              &(png_ptr->trans_color));
            else
                png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
                              NULL);
        }
    }
    #endif

    #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
        png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
                            PNG_FLAG_FILLER_AFTER | (png_ptr->flags & PNG_FLAG_STRIP_ALPHA));
    #endif

    #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
    {
        int rgb_error =
            png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info),
                               png_ptr->row_buf + 1);
        if (rgb_error)
        {
            png_ptr->rgb_to_gray_status = 1;
            if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
                PNG_RGB_TO_GRAY_WARN)
                png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
            if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
                PNG_RGB_TO_GRAY_ERR)
                png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
        }
    }
    #endif

    /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
     *
     *   In most cases, the "simple transparency" should be done prior to doing
     *   gray-to-RGB, or you will have to test 3x as many bytes to check if a
     *   pixel is transparent.  You would also need to make sure that the
     *   transparency information is upgraded to RGB.
     *
     *   To summarize, the current flow is:
     *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
     *                                   with background "in place" if transparent,
     *                                   convert to RGB if necessary
     *   - Gray + alpha -> composite with gray background and remove alpha bytes,
     *                                   convert to RGB if necessary
     *
     *   To support RGB backgrounds for gray images we need:
     *   - Gray + simple transparency -> convert to RGB + simple transparency,
     *                                   compare 3 or 6 bytes and composite with
     *                                   background "in place" if transparent
     *                                   (3x compare/pixel compared to doing
     *                                   composite with gray bkgrnd)
     *   - Gray + alpha -> convert to RGB + alpha, composite with background and
     *                                   remove alpha bytes (3x float
     *                                   operations/pixel compared with composite
     *                                   on gray background)
     *
     *  Greg's change will do this.  The reason it wasn't done before is for
     *  performance, as this increases the per-pixel operations.  If we would check
     *  in advance if the background was gray or RGB, and position the gray-to-RGB
     *  transform appropriately, then it would save a lot of work/time.
     */

    #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* If gray -> RGB, do so now only if background is non-gray; else do later
     * for performance reasons
     */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
        png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_BACKGROUND_SUPPORTED
    if ((png_ptr->transformations & PNG_BACKGROUND) &&
        ((png_ptr->num_trans != 0) ||
         (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)))
        png_do_background(&(png_ptr->row_info), png_ptr->row_buf + 1,
                          &(png_ptr->trans_color), &(png_ptr->background)
                          #ifdef PNG_READ_GAMMA_SUPPORTED
                          , &(png_ptr->background_1),
                          png_ptr->gamma_table, png_ptr->gamma_from_1,
                          png_ptr->gamma_to_1, png_ptr->gamma_16_table,
                          png_ptr->gamma_16_from_1, png_ptr->gamma_16_to_1,
                          png_ptr->gamma_shift
                          #endif
                          );
    #endif

    #ifdef PNG_READ_GAMMA_SUPPORTED
    if ((png_ptr->transformations & PNG_GAMMA) &&
        #ifdef PNG_READ_BACKGROUND_SUPPORTED
        !((png_ptr->transformations & PNG_BACKGROUND) &&
          ((png_ptr->num_trans != 0) ||
           (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
        #endif
        (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
        png_do_gamma(&(png_ptr->row_info), png_ptr->row_buf + 1,
                     png_ptr->gamma_table, png_ptr->gamma_16_table,
                     png_ptr->gamma_shift);
    #endif

    #ifdef PNG_READ_16_TO_8_SUPPORTED
    if (png_ptr->transformations & PNG_16_TO_8)
        png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_QUANTIZE_SUPPORTED
    if (png_ptr->transformations & PNG_QUANTIZE)
    {
        png_do_quantize((png_row_infop) & (png_ptr->row_info), png_ptr->row_buf + 1,
                        png_ptr->palette_lookup, png_ptr->quantize_index);
        if (png_ptr->row_info.rowbytes == (png_uint_32)0)
            png_error(png_ptr, "png_do_quantize returned rowbytes=0");
    }
    #endif

    #ifdef PNG_READ_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
        png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
        png_do_unshift(&(png_ptr->row_info), png_ptr->row_buf + 1,
                       &(png_ptr->shift));
    #endif

    #ifdef PNG_READ_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
        png_do_unpack(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
        png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
        png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* If gray -> RGB, do so now only if we did not do so above */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
        png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
        png_do_read_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
                           (png_uint_32)png_ptr->filler, png_ptr->flags);
    #endif

    #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_ALPHA)
        png_do_read_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
        png_do_read_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
        png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
    #endif

    #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
    {
        if (png_ptr->read_user_transform_fn != NULL)
            (*(png_ptr->read_user_transform_fn)) /* User read transform function */
                (png_ptr,                /* png_ptr */
                &(png_ptr->row_info),    /* row_info: */
                /*  png_uint_32 width;       width of row */
                /*  png_uint_32 rowbytes;    number of bytes in row */
                /*  png_byte color_type;     color type of pixels */
                /*  png_byte bit_depth;      bit depth of samples */
                /*  png_byte channels;       number of channels (1-4) */
                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
                png_ptr->row_buf + 1);   /* start of pixel data for row */
        #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
        if (png_ptr->user_transform_depth)
            png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
        if (png_ptr->user_transform_channels)
            png_ptr->row_info.channels = png_ptr->user_transform_channels;
        #endif
        png_ptr->row_info.pixel_depth = (png_byte)(png_ptr->row_info.bit_depth *
                                                   png_ptr->row_info.channels);
        png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
                                                  png_ptr->row_info.width);
    }
    #endif

}

    #ifdef PNG_READ_PACK_SUPPORTED
/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
 * without changing the actual values.  Thus, if you had a row with
 * a bit depth of 1, you would end up with bytes that only contained
 * the numbers 0 or 1.  If you would rather they contain 0 and 255, use
 * png_do_shift() after this.
 */
void /* PRIVATE */
png_do_unpack(png_row_infop row_info, png_bytep row)
{
    png_debug(1, "in png_do_unpack");

    if (row_info->bit_depth < 8)
    {
        png_uint_32 i;
        png_uint_32 row_width = row_info->width;

        switch (row_info->bit_depth)
        {
            case 1:
            {
                png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
                png_bytep dp = row + (png_size_t)row_width - 1;
                png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
                for (i = 0; i < row_width; i++)
                {
                    *dp = (png_byte)((*sp >> shift) & 0x01);
                    if (shift == 7)
                    {
                        shift = 0;
                        sp--;
                    }
                    else
                        shift++;

                    dp--;
                }
                break;
            }

            case 2:
            {

                png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
                png_bytep dp = row + (png_size_t)row_width - 1;
                png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                for (i = 0; i < row_width; i++)
                {
                    *dp = (png_byte)((*sp >> shift) & 0x03);
                    if (shift == 6)
                    {
                        shift = 0;
                        sp--;
                    }
                    else
                        shift += 2;

                    dp--;
                }
                break;
            }

            case 4:
            {
                png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
                png_bytep dp = row + (png_size_t)row_width - 1;
                png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
                for (i = 0; i < row_width; i++)
                {
                    *dp = (png_byte)((*sp >> shift) & 0x0f);
                    if (shift == 4)
                    {
                        shift = 0;
                        sp--;
                    }
                    else
                        shift = 4;

                    dp--;
                }
                break;
            }
        }
        row_info->bit_depth = 8;
        row_info->pixel_depth = (png_byte)(8 * row_info->channels);
        row_info->rowbytes = row_width * row_info->channels;
    }
}
    #endif

    #ifdef PNG_READ_SHIFT_SUPPORTED
/* Reverse the effects of png_do_shift.  This routine merely shifts the
 * pixels back to their significant bits values.  Thus, if you have
 * a row of bit depth 8, but only 5 are significant, this will shift
 * the values back to 0 through 31.
 */
void /* PRIVATE */
png_do_unshift(png_row_infop row_info, png_bytep row, png_color_8p sig_bits)
{
    png_debug(1, "in png_do_unshift");

    if (
        row_info->color_type != PNG_COLOR_TYPE_PALETTE)
    {
        int shift[4];
        int channels = 0;
        int c;
        png_uint_16 value = 0;
        png_uint_32 row_width = row_info->width;

        if (row_info->color_type & PNG_COLOR_MASK_COLOR)
        {
            shift[channels++] = row_info->bit_depth - sig_bits->red;
            shift[channels++] = row_info->bit_depth - sig_bits->green;
            shift[channels++] = row_info->bit_depth - sig_bits->blue;
        }
        else
        {
            shift[channels++] = row_info->bit_depth - sig_bits->gray;
        }
        if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
        {
            shift[channels++] = row_info->bit_depth - sig_bits->alpha;
        }

        for (c = 0; c < channels; c++)
        {
            if (shift[c] <= 0)
                shift[c] = 0;
            else
                value = 1;
        }

        if (!value)
            return;

        switch (row_info->bit_depth)
        {
            case 2:
            {
                png_bytep bp;
                png_uint_32 i;
                png_uint_32 istop = row_info->rowbytes;

                for (bp = row, i = 0; i < istop; i++)
                {
                    *bp >>= 1;
                    *bp++ &= 0x55;
                }
                break;
            }

            case 4:
            {
                png_bytep bp = row;
                png_uint_32 i;
                png_uint_32 istop = row_info->rowbytes;
                png_byte mask = (png_byte)((((int)0xf0 >> shift[0]) & (int)0xf0) |
                                           (png_byte)((int)0xf >> shift[0]));

                for (i = 0; i < istop; i++)
                {
                    *bp >>= shift[0];
                    *bp++ &= mask;
                }
                break;
            }

            case 8:
            {
                png_bytep bp = row;
                png_uint_32 i;
                png_uint_32 istop = row_width * channels;

                for (i = 0; i < istop; i++)
                {
                    *bp++ >>= shift[i % channels];
                }
                break;
            }

            case 16:
            {
                png_bytep bp = row;
                png_uint_32 i;
                png_uint_32 istop = channels * row_width;

                for (i = 0; i < istop; i++)
                {
                    value = (png_uint_16)((*bp << 8) + *(bp + 1));
                    value >>= shift[i % channels];
                    *bp++ = (png_byte)(value >> 8);
                    *bp++ = (png_byte)(value & 0xff);
                }
                break;
            }
        }
    }
}
    #endif

    #ifdef PNG_READ_16_TO_8_SUPPORTED
/* Chop rows of bit depth 16 down to 8 */
void /* PRIVATE */
png_do_chop(png_row_infop row_info, png_bytep row)
{
    png_debug(1, "in png_do_chop");

    if (row_info->bit_depth == 16)
    {
        png_bytep sp = row;
        png_bytep dp = row;
        png_uint_32 i;
        png_uint_32 istop = row_info->width * row_info->channels;

        for (i = 0; i < istop; i++, sp += 2, dp++)
        {
            #ifdef PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
            /* This does a more accurate scaling of the 16-bit color
             * value, rather than a simple low-byte truncation.
             *
             * What the ideal calculation should be:
             *   *dp = (((((png_uint_32)(*sp) << 8) |
             *          (png_uint_32)(*(sp + 1))) * 255 + 127)
             *          / (png_uint_32)65535L;
             *
             * GRR: no, I think this is what it really should be:
             *   *dp = (((((png_uint_32)(*sp) << 8) |
             *           (png_uint_32)(*(sp + 1))) + 128L)
             *           / (png_uint_32)257L;
             *
             * GRR: here's the exact calculation with shifts:
             *   temp = (((png_uint_32)(*sp) << 8) |
             *           (png_uint_32)(*(sp + 1))) + 128L;
             *   *dp = (temp - (temp >> 8)) >> 8;
             *
             * Approximate calculation with shift/add instead of multiply/divide:
             *   *dp = ((((png_uint_32)(*sp) << 8) |
             *          (png_uint_32)((int)(*(sp + 1)) - *sp)) + 128) >> 8;
             *
             * What we actually do to avoid extra shifting and conversion:
             */

            *dp = *sp + ((((int)(*(sp + 1)) - *sp) > 128) ? 1 : 0);
            #else
            /* Simply discard the low order byte */
            *dp = *sp;
            #endif
        }
        row_info->bit_depth = 8;
        row_info->pixel_depth = (png_byte)(8 * row_info->channels);
        row_info->rowbytes = row_info->width * row_info->channels;
    }
}
    #endif

    #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
void /* PRIVATE */
png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
{
    png_debug(1, "in png_do_read_swap_alpha");

    {
        png_uint_32 row_width = row_info->width;
        if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
        {
            /* This converts from RGBA to ARGB */
            if (row_info->bit_depth == 8)
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_byte save;
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    save = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = save;
                }
            }
            /* This converts from RRGGBBAA to AARRGGBB */
            else
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_byte save[2];
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    save[0] = *(--sp);
                    save[1] = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = save[0];
                    *(--dp) = save[1];
                }
            }
        }
        else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        {
            /* This converts from GA to AG */
            if (row_info->bit_depth == 8)
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_byte save;
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    save = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = save;
                }
            }
            /* This converts from GGAA to AAGG */
            else
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_byte save[2];
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    save[0] = *(--sp);
                    save[1] = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = save[0];
                    *(--dp) = save[1];
                }
            }
        }
    }
}
    #endif

    #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
void /* PRIVATE */
png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
{
    png_debug(1, "in png_do_read_invert_alpha");

    {
        png_uint_32 row_width = row_info->width;
        if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
        {
            /* This inverts the alpha channel in RGBA */
            if (row_info->bit_depth == 8)
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = (png_byte)(255 - *(--sp));

                    /*             This does nothing:
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                                   We can replace it with:
                     */
                    sp -= 3;
                    dp = sp;
                }
            }
            /* This inverts the alpha channel in RRGGBBAA */
            else
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = (png_byte)(255 - *(--sp));
                    *(--dp) = (png_byte)(255 - *(--sp));

                    /*             This does nothing:
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                                   We can replace it with:
                     */
                    sp -= 6;
                    dp = sp;
                }
            }
        }
        else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        {
            /* This inverts the alpha channel in GA */
            if (row_info->bit_depth == 8)
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = (png_byte)(255 - *(--sp));
                    *(--dp) = *(--sp);
                }
            }
            /* This inverts the alpha channel in GGAA */
            else
            {
                png_bytep sp = row + row_info->rowbytes;
                png_bytep dp = sp;
                png_uint_32 i;

                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = (png_byte)(255 - *(--sp));
                    *(--dp) = (png_byte)(255 - *(--sp));
                    /*
                     *(--dp) = *(--sp);
                     *(--dp) = *(--sp);
                     */
                    sp -= 2;
                    dp = sp;
                }
            }
        }
    }
}
    #endif

    #ifdef PNG_READ_FILLER_SUPPORTED
/* Add filler channel if we have RGB color */
void /* PRIVATE */
png_do_read_filler(png_row_infop row_info, png_bytep row,
                   png_uint_32 filler, png_uint_32 flags)
{
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;

    png_byte hi_filler = (png_byte)((filler >> 8) & 0xff);
    png_byte lo_filler = (png_byte)(filler & 0xff);

    png_debug(1, "in png_do_read_filler");

    if (
        row_info->color_type == PNG_COLOR_TYPE_GRAY)
    {
        if (row_info->bit_depth == 8)
        {
            /* This changes the data from G to GX */
            if (flags & PNG_FLAG_FILLER_AFTER)
            {
                png_bytep sp = row + (png_size_t)row_width;
                png_bytep dp = sp + (png_size_t)row_width;
                for (i = 1; i < row_width; i++)
                {
                    *(--dp) = lo_filler;
                    *(--dp) = *(--sp);
                }
                *(--dp) = lo_filler;
                row_info->channels = 2;
                row_info->pixel_depth = 16;
                row_info->rowbytes = row_width * 2;
            }
            /* This changes the data from G to XG */
            else
            {
                png_bytep sp = row + (png_size_t)row_width;
                png_bytep dp = sp + (png_size_t)row_width;
                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = *(--sp);
                    *(--dp) = lo_filler;
                }
                row_info->channels = 2;
                row_info->pixel_depth = 16;
                row_info->rowbytes = row_width * 2;
            }
        }
        else if (row_info->bit_depth == 16)
        {
            /* This changes the data from GG to GGXX */
            if (flags & PNG_FLAG_FILLER_AFTER)
            {
                png_bytep sp = row + (png_size_t)row_width * 2;
                png_bytep dp = sp + (png_size_t)row_width * 2;
                for (i = 1; i < row_width; i++)
                {
                    *(--dp) = hi_filler;
                    *(--dp) = lo_filler;
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                }
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
                row_info->channels = 2;
                row_info->pixel_depth = 32;
                row_info->rowbytes = row_width * 4;
            }
            /* This changes the data from GG to XXGG */
            else
            {
                png_bytep sp = row + (png_size_t)row_width * 2;
                png_bytep dp = sp + (png_size_t)row_width * 2;
                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = hi_filler;
                    *(--dp) = lo_filler;
                }
                row_info->channels = 2;
                row_info->pixel_depth = 32;
                row_info->rowbytes = row_width * 4;
            }
        }
    } /* COLOR_TYPE == GRAY */
    else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
    {
        if (row_info->bit_depth == 8)
        {
            /* This changes the data from RGB to RGBX */
            if (flags & PNG_FLAG_FILLER_AFTER)
            {
                png_bytep sp = row + (png_size_t)row_width * 3;
                png_bytep dp = sp + (png_size_t)row_width;
                for (i = 1; i < row_width; i++)
                {
                    *(--dp) = lo_filler;
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                }
                *(--dp) = lo_filler;
                row_info->channels = 4;
                row_info->pixel_depth = 32;
                row_info->rowbytes = row_width * 4;
            }
            /* This changes the data from RGB to XRGB */
            else
            {
                png_bytep sp = row + (png_size_t)row_width * 3;
                png_bytep dp = sp + (png_size_t)row_width;
                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = lo_filler;
                }
                row_info->channels = 4;
                row_info->pixel_depth = 32;
                row_info->rowbytes = row_width * 4;
            }
        }
        else if (row_info->bit_depth == 16)
        {
            /* This changes the data from RRGGBB to RRGGBBXX */
            if (flags & PNG_FLAG_FILLER_AFTER)
            {
                png_bytep sp = row + (png_size_t)row_width * 6;
                png_bytep dp = sp + (png_size_t)row_width * 2;
                for (i = 1; i < row_width; i++)
                {
                    *(--dp) = hi_filler;
                    *(--dp) = lo_filler;
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                }
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
                row_info->channels = 4;
                row_info->pixel_depth = 64;
                row_info->rowbytes = row_width * 8;
            }
            /* This changes the data from RRGGBB to XXRRGGBB */
            else
            {
                png_bytep sp = row + (png_size_t)row_width * 6;
                png_bytep dp = sp + (png_size_t)row_width * 2;
                for (i = 0; i < row_width; i++)
                {
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = *(--sp);
                    *(--dp) = hi_filler;
                    *(--dp) = lo_filler;
                }
                row_info->channels = 4;
                row_info->pixel_depth = 64;
                row_info->rowbytes = row_width * 8;
            }
        }
    } /* COLOR_TYPE == RGB */
}
    #endif

    #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
/* Expand grayscale files to RGB, with or without alpha */
void /* PRIVATE */
png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
{
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;

    png_debug(1, "in png_do_gray_to_rgb");

    if (row_info->bit_depth >= 8 &&
        !(row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
        if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
        {
            if (row_info->bit_depth == 8)
            {
                png_bytep sp = row + (png_size_t)row_width - 1;
                png_bytep dp = sp + (png_size_t)row_width * 2;
                for (i = 0; i < row_width; i++)
                {
                    *(dp--) = *sp;
                    *(dp--) = *sp;
                    *(dp--) = *(sp--);
                }
            }
            else
            {
                png_bytep sp = row + (png_size_t)row_width * 2 - 1;
                png_bytep dp = sp + (png_size_t)row_width * 4;
                for (i = 0; i < row_width; i++)
                {
                    *(dp--) = *sp;
                    *(dp--) = *(sp - 1);
                    *(dp--) = *sp;
                    *(dp--) = *(sp - 1);
                    *(dp--) = *(sp--);
                    *(dp--) = *(sp--);
                }
            }
        }
        else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        {
            if (row_info->bit_depth == 8)
            {
                png_bytep sp = row + (png_size_t)row_width * 2 - 1;
                png_bytep dp = sp + (png_size_t)row_width * 2;
                for (i = 0; i < row_width; i++)
                {
                    *(dp--) = *(sp--);
                    *(dp--) = *sp;
                    *(dp--) = *sp;
                    *(dp--) = *(sp--);
                }
            }
            else
            {
                png_bytep sp = row + (png_size_t)row_width * 4 - 1;
                png_bytep dp = sp + (png_size_t)row_width * 4;
                for (i = 0; i < row_width; i++)
                {
                    *(dp--) = *(sp--);
                    *(dp--) = *(sp--);
                    *(dp--) = *sp;
                    *(dp--) = *(sp - 1);
                    *(dp--) = *sp;
                    *(dp--) = *(sp - 1);
                    *(dp--) = *(sp--);
                    *(dp--) = *(sp--);
                }
            }
        }
        row_info->channels += (png_byte)2;
        row_info->color_type |= PNG_COLOR_MASK_COLOR;
        row_info->pixel_depth = (png_byte)(row_info->channels *
                                           row_info->bit_depth);
        row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
    }
}
    #endif

    #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
/* Reduce RGB files to grayscale, with or without alpha
 * using the equation given in Poynton's ColorFAQ at
 * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008)
 * New link:
 * <http://www.poynton.com/notes/colour_and_gamma/>
 * Charles Poynton poynton at poynton.com
 *
 *     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
 *
 *  We approximate this with
 *
 *     Y = 0.21268 * R    + 0.7151 * G    + 0.07217 * B
 *
 *  which can be expressed with integers as
 *
 *     Y = (6969 * R + 23434 * G + 2365 * B)/32768
 *
 *  The calculation is to be done in a linear colorspace.
 *
 *  Other integer coefficents can be used via png_set_rgb_to_gray().
 */
int /* PRIVATE */
png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)

{
    png_uint_32 i;

    png_uint_32 row_width = row_info->width;
    int rgb_error = 0;

    png_debug(1, "in png_do_rgb_to_gray");

    if (
        (row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
        png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
        png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
        png_uint_32 bc = png_ptr->rgb_to_gray_blue_coeff;

        if (row_info->color_type == PNG_COLOR_TYPE_RGB)
        {
            if (row_info->bit_depth == 8)
            {
                #if defined (PNG_READ_GAMMA_SUPPORTED) || defined (PNG_READ_BACKGROUND_SUPPORTED)
                if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
                {
                    png_bytep sp = row;
                    png_bytep dp = row;

                    for (i = 0; i < row_width; i++)
                    {
                        png_byte red = png_ptr->gamma_to_1[*(sp++)];
                        png_byte green = png_ptr->gamma_to_1[*(sp++)];
                        png_byte blue = png_ptr->gamma_to_1[*(sp++)];
                        if (red != green || red != blue)
                        {
                            rgb_error |= 1;
                            *(dp++) = png_ptr->gamma_from_1[
                                (rc * red + gc * green + bc * blue) >> 15];
                        }
                        else
                            *(dp++) = *(sp - 1);
                    }
                }
                else
                #endif
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_byte red = *(sp++);
                        png_byte green = *(sp++);
                        png_byte blue = *(sp++);
                        if (red != green || red != blue)
                        {
                            rgb_error |= 1;
                            *(dp++) = (png_byte)((rc * red + gc * green + bc * blue) >> 15);
                        }
                        else
                            *(dp++) = *(sp - 1);
                    }
                }
            }

            else /* RGB bit_depth == 16 */
            {
                #if defined (PNG_READ_GAMMA_SUPPORTED) || defined (PNG_READ_BACKGROUND_SUPPORTED)
                if (png_ptr->gamma_16_to_1 != NULL &&
                    png_ptr->gamma_16_from_1 != NULL)
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 red, green, blue, w;

                        red = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;
                        green = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;
                        blue = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;

                        if (red == green && red == blue)
                            w = red;
                        else
                        {
                            png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red & 0xff) >>
                                                                       png_ptr->gamma_shift][red >> 8];
                            png_uint_16 green_1 =
                                png_ptr->gamma_16_to_1[(green & 0xff) >>
                                                       png_ptr->gamma_shift][green >> 8];
                            png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue & 0xff) >>
                                                                        png_ptr->gamma_shift][blue >> 8];
                            png_uint_16 gray16 = (png_uint_16)((rc * red_1 + gc * green_1
                                                                + bc * blue_1) >> 15);
                            w = png_ptr->gamma_16_from_1[(gray16 & 0xff) >>
                                                         png_ptr->gamma_shift][gray16 >> 8];
                            rgb_error |= 1;
                        }

                        *(dp++) = (png_byte)((w >> 8) & 0xff);
                        *(dp++) = (png_byte)(w & 0xff);
                    }
                }
                else
                #endif
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 red, green, blue, gray16;

                        red = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;
                        green = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;
                        blue = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;

                        if (red != green || red != blue)
                            rgb_error |= 1;
                        gray16 = (png_uint_16)((rc * red + gc * green + bc * blue) >> 15);
                        *(dp++) = (png_byte)((gray16 >> 8) & 0xff);
                        *(dp++) = (png_byte)(gray16 & 0xff);
                    }
                }
            }
        }
        if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
        {
            if (row_info->bit_depth == 8)
            {
                #if defined (PNG_READ_GAMMA_SUPPORTED) || defined (PNG_READ_BACKGROUND_SUPPORTED)
                if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_byte red = png_ptr->gamma_to_1[*(sp++)];
                        png_byte green = png_ptr->gamma_to_1[*(sp++)];
                        png_byte blue = png_ptr->gamma_to_1[*(sp++)];
                        if (red != green || red != blue)
                            rgb_error |= 1;
                        *(dp++) = png_ptr->gamma_from_1
                                  [(rc * red + gc * green + bc * blue) >> 15];
                        *(dp++) = *(sp++); /* alpha */
                    }
                }
                else
                #endif
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_byte red = *(sp++);
                        png_byte green = *(sp++);
                        png_byte blue = *(sp++);
                        if (red != green || red != blue)
                            rgb_error |= 1;
                        *(dp++) = (png_byte)((rc * red + gc * green + bc * blue) >> 15);
                        *(dp++) = *(sp++); /* alpha */
                    }
                }
            }
            else /* RGBA bit_depth == 16 */
            {
                #if defined (PNG_READ_GAMMA_SUPPORTED) || defined (PNG_READ_BACKGROUND_SUPPORTED)
                if (png_ptr->gamma_16_to_1 != NULL &&
                    png_ptr->gamma_16_from_1 != NULL)
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 red, green, blue, w;

                        red = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;
                        green = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;
                        blue = (png_uint_16)(((*(sp)) << 8) | *(sp + 1)); sp += 2;

                        if (red == green && red == blue)
                            w = red;
                        else
                        {
                            png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red & 0xff) >>
                                                                       png_ptr->gamma_shift][red >> 8];
                            png_uint_16 green_1 =
                                png_ptr->gamma_16_to_1[(green & 0xff) >>
                                                       png_ptr->gamma_shift][green >> 8];
                            png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue & 0xff) >>
                                                                        png_ptr->gamma_shift][blue >> 8];
                            png_uint_16 gray16 = (png_uint_16)((rc * red_1
                                                                + gc * green_1 + bc * blue_1) >> 15);
                            w = png_ptr->gamma_16_from_1[(gray16 & 0xff) >>
                                                         png_ptr->gamma_shift][gray16 >> 8];
                            rgb_error |= 1;
                        }

                        *(dp++) = (png_byte)((w >> 8) & 0xff);
                        *(dp++) = (png_byte)(w & 0xff);
                        *(dp++) = *(sp++); /* alpha */
                        *(dp++) = *(sp++);
                    }
                }
                else
                #endif
                {
                    png_bytep sp = row;
                    png_bytep dp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 red, green, blue, gray16;
                        red = (png_uint_16)((*(sp) << 8) | *(sp + 1)); sp += 2;
                        green = (png_uint_16)((*(sp) << 8) | *(sp + 1)); sp += 2;
                        blue = (png_uint_16)((*(sp) << 8) | *(sp + 1)); sp += 2;
                        if (red != green || red != blue)
                            rgb_error |= 1;
                        gray16 = (png_uint_16)((rc * red + gc * green + bc * blue) >> 15);
                        *(dp++) = (png_byte)((gray16 >> 8) & 0xff);
                        *(dp++) = (png_byte)(gray16 & 0xff);
                        *(dp++) = *(sp++); /* alpha */
                        *(dp++) = *(sp++);
                    }
                }
            }
        }
        row_info->channels -= (png_byte)2;
        row_info->color_type &= ~PNG_COLOR_MASK_COLOR;
        row_info->pixel_depth = (png_byte)(row_info->channels *
                                           row_info->bit_depth);
        row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
    }
    return rgb_error;
}
    #endif

/* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth
 * large of png_color.  This lets grayscale images be treated as
 * paletted.  Most useful for gamma correction and simplification
 * of code.
 */
void PNGAPI
png_build_grayscale_palette(int bit_depth, png_colorp palette)
{
    int num_palette;
    int color_inc;
    int i;
    int v;

    png_debug(1, "in png_do_build_grayscale_palette");

    if (palette == NULL)
        return;

    switch (bit_depth)
    {
        case 1:
            num_palette = 2;
            color_inc = 0xff;
            break;

        case 2:
            num_palette = 4;
            color_inc = 0x55;
            break;

        case 4:
            num_palette = 16;
            color_inc = 0x11;
            break;

        case 8:
            num_palette = 256;
            color_inc = 1;
            break;

        default:
            num_palette = 0;
            color_inc = 0;
            break;
    }

    for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
    {
        palette[i].red = (png_byte)v;
        palette[i].green = (png_byte)v;
        palette[i].blue = (png_byte)v;
    }
}


    #ifdef PNG_READ_BACKGROUND_SUPPORTED
/* Replace any alpha or transparency with the supplied background color.
 * "background" is already in the screen gamma, while "background_1" is
 * at a gamma of 1.0.  Paletted files have already been taken care of.
 */
void /* PRIVATE */
png_do_background(png_row_infop row_info, png_bytep row,
                  png_color_16p trans_color, png_color_16p background
        #ifdef PNG_READ_GAMMA_SUPPORTED
                  , png_color_16p background_1,
                  png_bytep gamma_table, png_bytep gamma_from_1, png_bytep gamma_to_1,
                  png_uint_16pp gamma_16, png_uint_16pp gamma_16_from_1,
                  png_uint_16pp gamma_16_to_1, int gamma_shift
        #endif
                  )
{
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;
    int shift;

    png_debug(1, "in png_do_background");

    if (background != NULL &&
        (!(row_info->color_type & PNG_COLOR_MASK_ALPHA) ||
         (row_info->color_type != PNG_COLOR_TYPE_PALETTE && trans_color)))
    {
        switch (row_info->color_type)
        {
            case PNG_COLOR_TYPE_GRAY:
            {
                switch (row_info->bit_depth)
                {
                    case 1:
                    {
                        sp = row;
                        shift = 7;
                        for (i = 0; i < row_width; i++)
                        {
                            if ((png_uint_16)((*sp >> shift) & 0x01)
                                == trans_color->gray)
                            {
                                *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
                                *sp |= (png_byte)(background->gray << shift);
                            }
                            if (!shift)
                            {
                                shift = 7;
                                sp++;
                            }
                            else
                                shift--;
                        }
                        break;
                    }

                    case 2:
                    {
                        #ifdef PNG_READ_GAMMA_SUPPORTED
                        if (gamma_table != NULL)
                        {
                            sp = row;
                            shift = 6;
                            for (i = 0; i < row_width; i++)
                            {
                                if ((png_uint_16)((*sp >> shift) & 0x03)
                                    == trans_color->gray)
                                {
                                    *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
                                    *sp |= (png_byte)(background->gray << shift);
                                }
                                else
                                {
                                    png_byte p = (png_byte)((*sp >> shift) & 0x03);
                                    png_byte g = (png_byte)((gamma_table[p | (p << 2) |
                                                                         (p << 4) | (p << 6)] >> 6) & 0x03);
                                    *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
                                    *sp |= (png_byte)(g << shift);
                                }
                                if (!shift)
                                {
                                    shift = 6;
                                    sp++;
                                }
                                else
                                    shift -= 2;
                            }
                        }
                        else
                        #endif
                        {
                            sp = row;
                            shift = 6;
                            for (i = 0; i < row_width; i++)
                            {
                                if ((png_uint_16)((*sp >> shift) & 0x03)
                                    == trans_color->gray)
                                {
                                    *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
                                    *sp |= (png_byte)(background->gray << shift);
                                }
                                if (!shift)
                                {
                                    shift = 6;
                                    sp++;
                                }
                                else
                                    shift -= 2;
                            }
                        }
                        break;
                    }

                    case 4:
                    {
                        #ifdef PNG_READ_GAMMA_SUPPORTED
                        if (gamma_table != NULL)
                        {
                            sp = row;
                            shift = 4;
                            for (i = 0; i < row_width; i++)
                            {
                                if ((png_uint_16)((*sp >> shift) & 0x0f)
                                    == trans_color->gray)
                                {
                                    *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
                                    *sp |= (png_byte)(background->gray << shift);
                                }
                                else
                                {
                                    png_byte p = (png_byte)((*sp >> shift) & 0x0f);
                                    png_byte g = (png_byte)((gamma_table[p |
                                                                         (p << 4)] >> 4) & 0x0f);
                                    *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
                                    *sp |= (png_byte)(g << shift);
                                }
                                if (!shift)
                                {
                                    shift = 4;
                                    sp++;
                                }
                                else
                                    shift -= 4;
                            }
                        }
                        else
                        #endif
                        {
                            sp = row;
                            shift = 4;
                            for (i = 0; i < row_width; i++)
                            {
                                if ((png_uint_16)((*sp >> shift) & 0x0f)
                                    == trans_color->gray)
                                {
                                    *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
                                    *sp |= (png_byte)(background->gray << shift);
                                }
                                if (!shift)
                                {
                                    shift = 4;
                                    sp++;
                                }
                                else
                                    shift -= 4;
                            }
                        }
                        break;
                    }

                    case 8:
                    {
                        #ifdef PNG_READ_GAMMA_SUPPORTED
                        if (gamma_table != NULL)
                        {
                            sp = row;
                            for (i = 0; i < row_width; i++, sp++)
                            {
                                if (*sp == trans_color->gray)
                                {
                                    *sp = (png_byte)background->gray;
                                }
                                else
                                {
                                    *sp = gamma_table[*sp];
                                }
                            }
                        }
                        else
                        #endif
                        {
                            sp = row;
                            for (i = 0; i < row_width; i++, sp++)
                            {
                                if (*sp == trans_color->gray)
                                {
                                    *sp = (png_byte)background->gray;
                                }
                            }
                        }
                        break;
                    }

                    case 16:
                    {
                        #ifdef PNG_READ_GAMMA_SUPPORTED
                        if (gamma_16 != NULL)
                        {
                            sp = row;
                            for (i = 0; i < row_width; i++, sp += 2)
                            {
                                png_uint_16 v;

                                v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                                if (v == trans_color->gray)
                                {
                                    /* Background is already in screen gamma */
                                    *sp = (png_byte)((background->gray >> 8) & 0xff);
                                    *(sp + 1) = (png_byte)(background->gray & 0xff);
                                }
                                else
                                {
                                    v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                                    *sp = (png_byte)((v >> 8) & 0xff);
                                    *(sp + 1) = (png_byte)(v & 0xff);
                                }
                            }
                        }
                        else
                        #endif
                        {
                            sp = row;
                            for (i = 0; i < row_width; i++, sp += 2)
                            {
                                png_uint_16 v;

                                v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                                if (v == trans_color->gray)
                                {
                                    *sp = (png_byte)((background->gray >> 8) & 0xff);
                                    *(sp + 1) = (png_byte)(background->gray & 0xff);
                                }
                            }
                        }
                        break;
                    }
                }
                break;
            }

            case PNG_COLOR_TYPE_RGB:
            {
                if (row_info->bit_depth == 8)
                {
                    #ifdef PNG_READ_GAMMA_SUPPORTED
                    if (gamma_table != NULL)
                    {
                        sp = row;
                        for (i = 0; i < row_width; i++, sp += 3)
                        {
                            if (*sp == trans_color->red &&
                                *(sp + 1) == trans_color->green &&
                                *(sp + 2) == trans_color->blue)
                            {
                                *sp = (png_byte)background->red;
                                *(sp + 1) = (png_byte)background->green;
                                *(sp + 2) = (png_byte)background->blue;
                            }
                            else
                            {
                                *sp = gamma_table[*sp];
                                *(sp + 1) = gamma_table[*(sp + 1)];
                                *(sp + 2) = gamma_table[*(sp + 2)];
                            }
                        }
                    }
                    else
                    #endif
                    {
                        sp = row;
                        for (i = 0; i < row_width; i++, sp += 3)
                        {
                            if (*sp == trans_color->red &&
                                *(sp + 1) == trans_color->green &&
                                *(sp + 2) == trans_color->blue)
                            {
                                *sp = (png_byte)background->red;
                                *(sp + 1) = (png_byte)background->green;
                                *(sp + 2) = (png_byte)background->blue;
                            }
                        }
                    }
                }
                else /* if (row_info->bit_depth == 16) */
                {
                    #ifdef PNG_READ_GAMMA_SUPPORTED
                    if (gamma_16 != NULL)
                    {
                        sp = row;
                        for (i = 0; i < row_width; i++, sp += 6)
                        {
                            png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                            png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8) + *(sp + 3));
                            png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8) + *(sp + 5));
                            if (r == trans_color->red && g == trans_color->green &&
                                b == trans_color->blue)
                            {
                                /* Background is already in screen gamma */
                                *sp = (png_byte)((background->red >> 8) & 0xff);
                                *(sp + 1) = (png_byte)(background->red & 0xff);
                                *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
                                *(sp + 3) = (png_byte)(background->green & 0xff);
                                *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
                                *(sp + 5) = (png_byte)(background->blue & 0xff);
                            }
                            else
                            {
                                png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                                *sp = (png_byte)((v >> 8) & 0xff);
                                *(sp + 1) = (png_byte)(v & 0xff);
                                v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
                                *(sp + 2) = (png_byte)((v >> 8) & 0xff);
                                *(sp + 3) = (png_byte)(v & 0xff);
                                v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
                                *(sp + 4) = (png_byte)((v >> 8) & 0xff);
                                *(sp + 5) = (png_byte)(v & 0xff);
                            }
                        }
                    }
                    else
                    #endif
                    {
                        sp = row;
                        for (i = 0; i < row_width; i++, sp += 6)
                        {
                            png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                            png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8) + *(sp + 3));
                            png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8) + *(sp + 5));

                            if (r == trans_color->red && g == trans_color->green &&
                                b == trans_color->blue)
                            {
                                *sp = (png_byte)((background->red >> 8) & 0xff);
                                *(sp + 1) = (png_byte)(background->red & 0xff);
                                *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
                                *(sp + 3) = (png_byte)(background->green & 0xff);
                                *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
                                *(sp + 5) = (png_byte)(background->blue & 0xff);
                            }
                        }
                    }
                }
                break;
            }

            case PNG_COLOR_TYPE_GRAY_ALPHA:
            {
                if (row_info->bit_depth == 8)
                {
                    #ifdef PNG_READ_GAMMA_SUPPORTED
                    if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                        gamma_table != NULL)
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 2, dp++)
                        {
                            png_uint_16 a = *(sp + 1);

                            if (a == 0xff)
                            {
                                *dp = gamma_table[*sp];
                            }
                            else if (a == 0)
                            {
                                /* Background is already in screen gamma */
                                *dp = (png_byte)background->gray;
                            }
                            else
                            {
                                png_byte v, w;

                                v = gamma_to_1[*sp];
                                png_composite(w, v, a, background_1->gray);
                                *dp = gamma_from_1[w];
                            }
                        }
                    }
                    else
                    #endif
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 2, dp++)
                        {
                            png_byte a = *(sp + 1);

                            if (a == 0xff)
                            {
                                *dp = *sp;
                            }
                            #ifdef PNG_READ_GAMMA_SUPPORTED
                            else if (a == 0)
                            {
                                *dp = (png_byte)background->gray;
                            }
                            else
                            {
                                png_composite(*dp, *sp, a, background_1->gray);
                            }
                            #else
                            *dp = (png_byte)background->gray;
                            #endif
                        }
                    }
                }
                else /* if (png_ptr->bit_depth == 16) */
                {
                    #ifdef PNG_READ_GAMMA_SUPPORTED
                    if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                        gamma_16_to_1 != NULL)
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 4, dp += 2)
                        {
                            png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8) + *(sp + 3));

                            if (a == (png_uint_16)0xffff)
                            {
                                png_uint_16 v;

                                v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                                *dp = (png_byte)((v >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(v & 0xff);
                            }
                            #ifdef PNG_READ_GAMMA_SUPPORTED
                            else if (a == 0)
                            #else
                            else
                            #endif
                            {
                                /* Background is already in screen gamma */
                                *dp = (png_byte)((background->gray >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(background->gray & 0xff);
                            }
                            #ifdef PNG_READ_GAMMA_SUPPORTED
                            else
                            {
                                png_uint_16 g, v, w;

                                g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
                                png_composite_16(v, g, a, background_1->gray);
                                w = gamma_16_from_1[(v & 0xff) >> gamma_shift][v >> 8];
                                *dp = (png_byte)((w >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(w & 0xff);
                            }
                            #endif
                        }
                    }
                    else
                    #endif
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 4, dp += 2)
                        {
                            png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8) + *(sp + 3));
                            if (a == (png_uint_16)0xffff)
                            {
                                png_memcpy(dp, sp, 2);
                            }
                            #ifdef PNG_READ_GAMMA_SUPPORTED
                            else if (a == 0)
                            #else
                            else
                            #endif
                            {
                                *dp = (png_byte)((background->gray >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(background->gray & 0xff);
                            }
                            #ifdef PNG_READ_GAMMA_SUPPORTED
                            else
                            {
                                png_uint_16 g, v;

                                g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                                png_composite_16(v, g, a, background_1->gray);
                                *dp = (png_byte)((v >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(v & 0xff);
                            }
                            #endif
                        }
                    }
                }
                break;
            }

            case PNG_COLOR_TYPE_RGB_ALPHA:
            {
                if (row_info->bit_depth == 8)
                {
                    #ifdef PNG_READ_GAMMA_SUPPORTED
                    if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                        gamma_table != NULL)
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                        {
                            png_byte a = *(sp + 3);

                            if (a == 0xff)
                            {
                                *dp = gamma_table[*sp];
                                *(dp + 1) = gamma_table[*(sp + 1)];
                                *(dp + 2) = gamma_table[*(sp + 2)];
                            }
                            else if (a == 0)
                            {
                                /* Background is already in screen gamma */
                                *dp = (png_byte)background->red;
                                *(dp + 1) = (png_byte)background->green;
                                *(dp + 2) = (png_byte)background->blue;
                            }
                            else
                            {
                                png_byte v, w;

                                v = gamma_to_1[*sp];
                                png_composite(w, v, a, background_1->red);
                                *dp = gamma_from_1[w];
                                v = gamma_to_1[*(sp + 1)];
                                png_composite(w, v, a, background_1->green);
                                *(dp + 1) = gamma_from_1[w];
                                v = gamma_to_1[*(sp + 2)];
                                png_composite(w, v, a, background_1->blue);
                                *(dp + 2) = gamma_from_1[w];
                            }
                        }
                    }
                    else
                    #endif
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                        {
                            png_byte a = *(sp + 3);

                            if (a == 0xff)
                            {
                                *dp = *sp;
                                *(dp + 1) = *(sp + 1);
                                *(dp + 2) = *(sp + 2);
                            }
                            else if (a == 0)
                            {
                                *dp = (png_byte)background->red;
                                *(dp + 1) = (png_byte)background->green;
                                *(dp + 2) = (png_byte)background->blue;
                            }
                            else
                            {
                                png_composite(*dp, *sp, a, background->red);
                                png_composite(*(dp + 1), *(sp + 1), a,
                                              background->green);
                                png_composite(*(dp + 2), *(sp + 2), a,
                                              background->blue);
                            }
                        }
                    }
                }
                else /* if (row_info->bit_depth == 16) */
                {
                    #ifdef PNG_READ_GAMMA_SUPPORTED
                    if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                        gamma_16_to_1 != NULL)
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 8, dp += 6)
                        {
                            png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
                                                           << 8) + (png_uint_16)(*(sp + 7)));
                            if (a == (png_uint_16)0xffff)
                            {
                                png_uint_16 v;

                                v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                                *dp = (png_byte)((v >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(v & 0xff);
                                v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
                                *(dp + 2) = (png_byte)((v >> 8) & 0xff);
                                *(dp + 3) = (png_byte)(v & 0xff);
                                v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
                                *(dp + 4) = (png_byte)((v >> 8) & 0xff);
                                *(dp + 5) = (png_byte)(v & 0xff);
                            }
                            else if (a == 0)
                            {
                                /* Background is already in screen gamma */
                                *dp = (png_byte)((background->red >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(background->red & 0xff);
                                *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
                                *(dp + 3) = (png_byte)(background->green & 0xff);
                                *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
                                *(dp + 5) = (png_byte)(background->blue & 0xff);
                            }
                            else
                            {
                                png_uint_16 v, w, x;

                                v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
                                png_composite_16(w, v, a, background_1->red);
                                x = gamma_16_from_1[((w & 0xff) >> gamma_shift)][w >> 8];
                                *dp = (png_byte)((x >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(x & 0xff);
                                v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
                                png_composite_16(w, v, a, background_1->green);
                                x = gamma_16_from_1[((w & 0xff) >> gamma_shift)][w >> 8];
                                *(dp + 2) = (png_byte)((x >> 8) & 0xff);
                                *(dp + 3) = (png_byte)(x & 0xff);
                                v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
                                png_composite_16(w, v, a, background_1->blue);
                                x = gamma_16_from_1[(w & 0xff) >> gamma_shift][w >> 8];
                                *(dp + 4) = (png_byte)((x >> 8) & 0xff);
                                *(dp + 5) = (png_byte)(x & 0xff);
                            }
                        }
                    }
                    else
                    #endif
                    {
                        sp = row;
                        dp = row;
                        for (i = 0; i < row_width; i++, sp += 8, dp += 6)
                        {
                            png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
                                                           << 8) + (png_uint_16)(*(sp + 7)));
                            if (a == (png_uint_16)0xffff)
                            {
                                png_memcpy(dp, sp, 6);
                            }
                            else if (a == 0)
                            {
                                *dp = (png_byte)((background->red >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(background->red & 0xff);
                                *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
                                *(dp + 3) = (png_byte)(background->green & 0xff);
                                *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
                                *(dp + 5) = (png_byte)(background->blue & 0xff);
                            }
                            else
                            {
                                png_uint_16 v;

                                png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                                png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
                                                              + *(sp + 3));
                                png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                                                              + *(sp + 5));

                                png_composite_16(v, r, a, background->red);
                                *dp = (png_byte)((v >> 8) & 0xff);
                                *(dp + 1) = (png_byte)(v & 0xff);
                                png_composite_16(v, g, a, background->green);
                                *(dp + 2) = (png_byte)((v >> 8) & 0xff);
                                *(dp + 3) = (png_byte)(v & 0xff);
                                png_composite_16(v, b, a, background->blue);
                                *(dp + 4) = (png_byte)((v >> 8) & 0xff);
                                *(dp + 5) = (png_byte)(v & 0xff);
                            }
                        }
                    }
                }
                break;
            }
        }

        if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
        {
            row_info->color_type &= ~PNG_COLOR_MASK_ALPHA;
            row_info->channels--;
            row_info->pixel_depth = (png_byte)(row_info->channels *
                                               row_info->bit_depth);
            row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
        }
    }
}
    #endif

    #ifdef PNG_READ_GAMMA_SUPPORTED
/* Gamma correct the image, avoiding the alpha channel.  Make sure
 * you do this after you deal with the transparency issue on grayscale
 * or RGB images. If your bit depth is 8, use gamma_table, if it
 * is 16, use gamma_16_table and gamma_shift.  Build these with
 * build_gamma_table().
 */
void /* PRIVATE */
png_do_gamma(png_row_infop row_info, png_bytep row,
             png_bytep gamma_table, png_uint_16pp gamma_16_table,
             int gamma_shift)
{
    png_bytep sp;
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;

    png_debug(1, "in png_do_gamma");

    if (
        ((row_info->bit_depth <= 8 && gamma_table != NULL) ||
         (row_info->bit_depth == 16 && gamma_16_table != NULL)))
    {
        switch (row_info->color_type)
        {
            case PNG_COLOR_TYPE_RGB:
            {
                if (row_info->bit_depth == 8)
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        *sp = gamma_table[*sp];
                        sp++;
                        *sp = gamma_table[*sp];
                        sp++;
                        *sp = gamma_table[*sp];
                        sp++;
                    }
                }
                else /* if (row_info->bit_depth == 16) */
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 v;

                        v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 2;
                        v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 2;
                        v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 2;
                    }
                }
                break;
            }

            case PNG_COLOR_TYPE_RGB_ALPHA:
            {
                if (row_info->bit_depth == 8)
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        *sp = gamma_table[*sp];
                        sp++;
                        *sp = gamma_table[*sp];
                        sp++;
                        *sp = gamma_table[*sp];
                        sp++;
                        sp++;
                    }
                }
                else /* if (row_info->bit_depth == 16) */
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 2;
                        v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 2;
                        v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 4;
                    }
                }
                break;
            }

            case PNG_COLOR_TYPE_GRAY_ALPHA:
            {
                if (row_info->bit_depth == 8)
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        *sp = gamma_table[*sp];
                        sp += 2;
                    }
                }
                else /* if (row_info->bit_depth == 16) */
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 4;
                    }
                }
                break;
            }

            case PNG_COLOR_TYPE_GRAY:
            {
                if (row_info->bit_depth == 2)
                {
                    sp = row;
                    for (i = 0; i < row_width; i += 4)
                    {
                        int a = *sp & 0xc0;
                        int b = *sp & 0x30;
                        int c = *sp & 0x0c;
                        int d = *sp & 0x03;

                        *sp = (png_byte)(
                            ((((int)gamma_table[a | (a >> 2) | (a >> 4) | (a >> 6)])) & 0xc0) |
                            ((((int)gamma_table[(b << 2) | b | (b >> 2) | (b >> 4)]) >> 2) & 0x30) |
                            ((((int)gamma_table[(c << 4) | (c << 2) | c | (c >> 2)]) >> 4) & 0x0c) |
                            ((((int)gamma_table[(d << 6) | (d << 4) | (d << 2) | d]) >> 6)));
                        sp++;
                    }
                }

                if (row_info->bit_depth == 4)
                {
                    sp = row;
                    for (i = 0; i < row_width; i += 2)
                    {
                        int msb = *sp & 0xf0;
                        int lsb = *sp & 0x0f;

                        *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
                                         | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
                        sp++;
                    }
                }

                else if (row_info->bit_depth == 8)
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        *sp = gamma_table[*sp];
                        sp++;
                    }
                }

                else if (row_info->bit_depth == 16)
                {
                    sp = row;
                    for (i = 0; i < row_width; i++)
                    {
                        png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                        *sp = (png_byte)((v >> 8) & 0xff);
                        *(sp + 1) = (png_byte)(v & 0xff);
                        sp += 2;
                    }
                }
                break;
            }
        }
    }
}
    #endif

    #ifdef PNG_READ_EXPAND_SUPPORTED
/* Expands a palette row to an RGB or RGBA row depending
 * upon whether you supply trans and num_trans.
 */
void /* PRIVATE */
png_do_expand_palette(png_row_infop row_info, png_bytep row,
                      png_colorp palette, png_bytep trans_alpha, int num_trans)
{
    int shift, value;
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;

    png_debug(1, "in png_do_expand_palette");

    if (
        row_info->color_type == PNG_COLOR_TYPE_PALETTE)
    {
        if (row_info->bit_depth < 8)
        {
            switch (row_info->bit_depth)
            {
                case 1:
                {
                    sp = row + (png_size_t)((row_width - 1) >> 3);
                    dp = row + (png_size_t)row_width - 1;
                    shift = 7 - (int)((row_width + 7) & 0x07);
                    for (i = 0; i < row_width; i++)
                    {
                        if ((*sp >> shift) & 0x01)
                            *dp = 1;
                        else
                            *dp = 0;
                        if (shift == 7)
                        {
                            shift = 0;
                            sp--;
                        }
                        else
                            shift++;

                        dp--;
                    }
                    break;
                }

                case 2:
                {
                    sp = row + (png_size_t)((row_width - 1) >> 2);
                    dp = row + (png_size_t)row_width - 1;
                    shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                    for (i = 0; i < row_width; i++)
                    {
                        value = (*sp >> shift) & 0x03;
                        *dp = (png_byte)value;
                        if (shift == 6)
                        {
                            shift = 0;
                            sp--;
                        }
                        else
                            shift += 2;

                        dp--;
                    }
                    break;
                }

                case 4:
                {
                    sp = row + (png_size_t)((row_width - 1) >> 1);
                    dp = row + (png_size_t)row_width - 1;
                    shift = (int)((row_width & 0x01) << 2);
                    for (i = 0; i < row_width; i++)
                    {
                        value = (*sp >> shift) & 0x0f;
                        *dp = (png_byte)value;
                        if (shift == 4)
                        {
                            shift = 0;
                            sp--;
                        }
                        else
                            shift += 4;

                        dp--;
                    }
                    break;
                }
            }
            row_info->bit_depth = 8;
            row_info->pixel_depth = 8;
            row_info->rowbytes = row_width;
        }
        switch (row_info->bit_depth)
        {
            case 8:
            {
                if (trans_alpha != NULL)
                {
                    sp = row + (png_size_t)row_width - 1;
                    dp = row + (png_size_t)(row_width << 2) - 1;

                    for (i = 0; i < row_width; i++)
                    {
                        if ((int)(*sp) >= num_trans)
                            *dp-- = 0xff;
                        else
                            *dp-- = trans_alpha[*sp];
                        *dp-- = palette[*sp].blue;
                        *dp-- = palette[*sp].green;
                        *dp-- = palette[*sp].red;
                        sp--;
                    }
                    row_info->bit_depth = 8;
                    row_info->pixel_depth = 32;
                    row_info->rowbytes = row_width * 4;
                    row_info->color_type = 6;
                    row_info->channels = 4;
                }
                else
                {
                    sp = row + (png_size_t)row_width - 1;
                    dp = row + (png_size_t)(row_width * 3) - 1;

                    for (i = 0; i < row_width; i++)
                    {
                        *dp-- = palette[*sp].blue;
                        *dp-- = palette[*sp].green;
                        *dp-- = palette[*sp].red;
                        sp--;
                    }

                    row_info->bit_depth = 8;
                    row_info->pixel_depth = 24;
                    row_info->rowbytes = row_width * 3;
                    row_info->color_type = 2;
                    row_info->channels = 3;
                }
                break;
            }
        }
    }
}

/* If the bit depth < 8, it is expanded to 8.  Also, if the already
 * expanded transparency value is supplied, an alpha channel is built.
 */
void /* PRIVATE */
png_do_expand(png_row_infop row_info, png_bytep row,
              png_color_16p trans_value)
{
    int shift, value;
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;

    png_debug(1, "in png_do_expand");

    {
        if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
        {
            png_uint_16 gray = (png_uint_16)(trans_value ? trans_value->gray : 0);

            if (row_info->bit_depth < 8)
            {
                switch (row_info->bit_depth)
                {
                    case 1:
                    {
                        gray = (png_uint_16)((gray & 0x01) * 0xff);
                        sp = row + (png_size_t)((row_width - 1) >> 3);
                        dp = row + (png_size_t)row_width - 1;
                        shift = 7 - (int)((row_width + 7) & 0x07);
                        for (i = 0; i < row_width; i++)
                        {
                            if ((*sp >> shift) & 0x01)
                                *dp = 0xff;
                            else
                                *dp = 0;
                            if (shift == 7)
                            {
                                shift = 0;
                                sp--;
                            }
                            else
                                shift++;

                            dp--;
                        }
                        break;
                    }

                    case 2:
                    {
                        gray = (png_uint_16)((gray & 0x03) * 0x55);
                        sp = row + (png_size_t)((row_width - 1) >> 2);
                        dp = row + (png_size_t)row_width - 1;
                        shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                        for (i = 0; i < row_width; i++)
                        {
                            value = (*sp >> shift) & 0x03;
                            *dp = (png_byte)(value | (value << 2) | (value << 4) |
                                             (value << 6));
                            if (shift == 6)
                            {
                                shift = 0;
                                sp--;
                            }
                            else
                                shift += 2;

                            dp--;
                        }
                        break;
                    }

                    case 4:
                    {
                        gray = (png_uint_16)((gray & 0x0f) * 0x11);
                        sp = row + (png_size_t)((row_width - 1) >> 1);
                        dp = row + (png_size_t)row_width - 1;
                        shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
                        for (i = 0; i < row_width; i++)
                        {
                            value = (*sp >> shift) & 0x0f;
                            *dp = (png_byte)(value | (value << 4));
                            if (shift == 4)
                            {
                                shift = 0;
                                sp--;
                            }
                            else
                                shift = 4;

                            dp--;
                        }
                        break;
                    }
                }

                row_info->bit_depth = 8;
                row_info->pixel_depth = 8;
                row_info->rowbytes = row_width;
            }

            if (trans_value != NULL)
            {
                if (row_info->bit_depth == 8)
                {
                    gray = gray & 0xff;
                    sp = row + (png_size_t)row_width - 1;
                    dp = row + (png_size_t)(row_width << 1) - 1;
                    for (i = 0; i < row_width; i++)
                    {
                        if (*sp == gray)
                            *dp-- = 0;
                        else
                            *dp-- = 0xff;
                        *dp-- = *sp--;
                    }
                }

                else if (row_info->bit_depth == 16)
                {
                    png_byte gray_high = (gray >> 8) & 0xff;
                    png_byte gray_low = gray & 0xff;
                    sp = row + row_info->rowbytes - 1;
                    dp = row + (row_info->rowbytes << 1) - 1;
                    for (i = 0; i < row_width; i++)
                    {
                        if (*(sp - 1) == gray_high && *(sp) == gray_low)
                        {
                            *dp-- = 0;
                            *dp-- = 0;
                        }
                        else
                        {
                            *dp-- = 0xff;
                            *dp-- = 0xff;
                        }
                        *dp-- = *sp--;
                        *dp-- = *sp--;
                    }
                }

                row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
                row_info->channels = 2;
                row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
                row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
                                                  row_width);
            }
        }
        else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_value)
        {
            if (row_info->bit_depth == 8)
            {
                png_byte red = trans_value->red & 0xff;
                png_byte green = trans_value->green & 0xff;
                png_byte blue = trans_value->blue & 0xff;
                sp = row + (png_size_t)row_info->rowbytes - 1;
                dp = row + (png_size_t)(row_width << 2) - 1;
                for (i = 0; i < row_width; i++)
                {
                    if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)
                        *dp-- = 0;
                    else
                        *dp-- = 0xff;
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                }
            }
            else if (row_info->bit_depth == 16)
            {
                png_byte red_high = (trans_value->red >> 8) & 0xff;
                png_byte green_high = (trans_value->green >> 8) & 0xff;
                png_byte blue_high = (trans_value->blue >> 8) & 0xff;
                png_byte red_low = trans_value->red & 0xff;
                png_byte green_low = trans_value->green & 0xff;
                png_byte blue_low = trans_value->blue & 0xff;
                sp = row + row_info->rowbytes - 1;
                dp = row + (png_size_t)(row_width << 3) - 1;
                for (i = 0; i < row_width; i++)
                {
                    if (*(sp - 5) == red_high &&
                        *(sp - 4) == red_low &&
                        *(sp - 3) == green_high &&
                        *(sp - 2) == green_low &&
                        *(sp - 1) == blue_high &&
                        *(sp) == blue_low)
                    {
                        *dp-- = 0;
                        *dp-- = 0;
                    }
                    else
                    {
                        *dp-- = 0xff;
                        *dp-- = 0xff;
                    }
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                    *dp-- = *sp--;
                }
            }
            row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
            row_info->channels = 4;
            row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);
            row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
        }
    }
}
    #endif

    #ifdef PNG_READ_QUANTIZE_SUPPORTED
void /* PRIVATE */
png_do_quantize(png_row_infop row_info, png_bytep row,
                png_bytep palette_lookup, png_bytep quantize_lookup)
{
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;

    png_debug(1, "in png_do_quantize");

    {
        if (row_info->color_type == PNG_COLOR_TYPE_RGB &&
            palette_lookup && row_info->bit_depth == 8)
        {
            int r, g, b, p;
            sp = row;
            dp = row;
            for (i = 0; i < row_width; i++)
            {
                r = *sp++;
                g = *sp++;
                b = *sp++;

                /* This looks real messy, but the compiler will reduce
                 * it down to a reasonable formula.  For example, with
                 * 5 bits per color, we get:
                 * p = (((r >> 3) & 0x1f) << 10) |
                 *    (((g >> 3) & 0x1f) << 5) |
                 *    ((b >> 3) & 0x1f);
                 */
                p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                      ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                     (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                    (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                      ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                     (PNG_QUANTIZE_BLUE_BITS)) |
                    ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                     ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

                *dp++ = palette_lookup[p];
            }
            row_info->color_type = PNG_COLOR_TYPE_PALETTE;
            row_info->channels = 1;
            row_info->pixel_depth = row_info->bit_depth;
            row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
        }
        else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
                 palette_lookup != NULL && row_info->bit_depth == 8)
        {
            int r, g, b, p;
            sp = row;
            dp = row;
            for (i = 0; i < row_width; i++)
            {
                r = *sp++;
                g = *sp++;
                b = *sp++;
                sp++;

                p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                      ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                     (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                    (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                      ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                     (PNG_QUANTIZE_BLUE_BITS)) |
                    ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                     ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

                *dp++ = palette_lookup[p];
            }
            row_info->color_type = PNG_COLOR_TYPE_PALETTE;
            row_info->channels = 1;
            row_info->pixel_depth = row_info->bit_depth;
            row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
        }
        else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
                 quantize_lookup && row_info->bit_depth == 8)
        {
            sp = row;
            for (i = 0; i < row_width; i++, sp++)
            {
                *sp = quantize_lookup[*sp];
            }
        }
    }
}
    #endif

    #ifdef PNG_FLOATING_POINT_SUPPORTED
        #ifdef PNG_READ_GAMMA_SUPPORTED
static PNG_CONST int png_gamma_shift[] =
{ 0x10, 0x21, 0x42, 0x84, 0x110, 0x248, 0x550, 0xff0, 0x00 };

/* We build the 8- or 16-bit gamma tables here.  Note that for 16-bit
 * tables, we don't make a full table if we are reducing to 8-bit in
 * the future.  Note also how the gamma_16 tables are segmented so that
 * we don't need to allocate > 64K chunks for a full 16-bit table.
 *
 * See the PNG extensions document for an integer algorithm for creating
 * the gamma tables.  Maybe we will implement that here someday.
 *
 * We should only reach this point if
 *
 *      the file_gamma is known (i.e., the gAMA or sRGB chunk is present,
 *      or the application has provided a file_gamma)
 *
 *   AND
 *      {
 *         the screen_gamma is known
 *
 *      OR
 *
 *         RGB_to_gray transformation is being performed
 *      }
 *
 *   AND
 *      {
 *         the screen_gamma is different from the reciprocal of the
 *         file_gamma by more than the specified threshold
 *
 *      OR
 *
 *         a background color has been specified and the file_gamma
 *         and screen_gamma are not 1.0, within the specified threshold.
 *      }
 */

void /* PRIVATE */
png_build_gamma_table(png_structp png_ptr, png_byte bit_depth)
{
    png_debug(1, "in png_build_gamma_table");

    if (bit_depth <= 8)
    {
        int i;
        double g;

        if (png_ptr->screen_gamma > .000001)
            g = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);

        else
            g = 1.0;

        png_ptr->gamma_table = (png_bytep)png_malloc(png_ptr,
                                                     (png_uint_32)256);

        for (i = 0; i < 256; i++)
        {
            png_ptr->gamma_table[i] = (png_byte)(pow((double)i / 255.0,
                                                     g) * 255.0 + .5);
        }

        #if defined (PNG_READ_BACKGROUND_SUPPORTED) || \
        defined (PNG_READ_RGB_TO_GRAY_SUPPORTED)
        if (png_ptr->transformations & ((PNG_BACKGROUND) | PNG_RGB_TO_GRAY))
        {

            g = 1.0 / (png_ptr->gamma);

            png_ptr->gamma_to_1 = (png_bytep)png_malloc(png_ptr,
                                                        (png_uint_32)256);

            for (i = 0; i < 256; i++)
            {
                png_ptr->gamma_to_1[i] = (png_byte)(pow((double)i / 255.0,
                                                        g) * 255.0 + .5);
            }


            png_ptr->gamma_from_1 = (png_bytep)png_malloc(png_ptr,
                                                          (png_uint_32)256);

            if (png_ptr->screen_gamma > 0.000001)
                g = 1.0 / png_ptr->screen_gamma;

            else
                g = png_ptr->gamma; /* Probably doing rgb_to_gray */

            for (i = 0; i < 256; i++)
            {
                png_ptr->gamma_from_1[i] = (png_byte)(pow((double)i / 255.0,
                                                          g) * 255.0 + .5);

            }
        }
        #endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_RGB_TO_GRAY_SUPPORTED */
    }
    else
    {
        double g;
        int i, j, shift, num;
        int sig_bit;
        png_uint_32 ig;

        if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
        {
            sig_bit = (int)png_ptr->sig_bit.red;

            if ((int)png_ptr->sig_bit.green > sig_bit)
                sig_bit = png_ptr->sig_bit.green;

            if ((int)png_ptr->sig_bit.blue > sig_bit)
                sig_bit = png_ptr->sig_bit.blue;
        }
        else
        {
            sig_bit = (int)png_ptr->sig_bit.gray;
        }

        if (sig_bit > 0)
            shift = 16 - sig_bit;

        else
            shift = 0;

        if (png_ptr->transformations & PNG_16_TO_8)
        {
            if (shift < (16 - PNG_MAX_GAMMA_8))
                shift = (16 - PNG_MAX_GAMMA_8);
        }

        if (shift > 8)
            shift = 8;

        if (shift < 0)
            shift = 0;

        png_ptr->gamma_shift = (png_byte)shift;

        num = (1 << (8 - shift));

        if (png_ptr->screen_gamma > .000001)
            g = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
        else
            g = 1.0;

        png_ptr->gamma_16_table = (png_uint_16pp)png_calloc(png_ptr,
                                                            (png_uint_32)(num * png_sizeof(png_uint_16p)));

        if (png_ptr->transformations & (PNG_16_TO_8 | PNG_BACKGROUND))
        {
            double fin, fout;
            png_uint_32 last, max;

            for (i = 0; i < num; i++)
            {
                png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr,
                                                                      (png_uint_32)(256 * png_sizeof(png_uint_16)));
            }

            g = 1.0 / g;
            last = 0;
            for (i = 0; i < 256; i++)
            {
                fout = ((double)i + 0.5) / 256.0;
                fin = pow(fout, g);
                max = (png_uint_32)(fin * (double)((png_uint_32)num << 8));
                while (last <= max)
                {
                    png_ptr->gamma_16_table[(int)(last & (0xff >> shift))]
                    [(int)(last >> (8 - shift))] = (png_uint_16)(
                        (png_uint_16)i | ((png_uint_16)i << 8));
                    last++;
                }
            }
            while (last < ((png_uint_32)num << 8))
            {
                png_ptr->gamma_16_table[(int)(last & (0xff >> shift))]
                [(int)(last >> (8 - shift))] = (png_uint_16)65535L;
                last++;
            }
        }
        else
        {
            for (i = 0; i < num; i++)
            {
                png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr,
                                                                      (png_uint_32)(256 * png_sizeof(png_uint_16)));

                ig = (((png_uint_32)i * (png_uint_32)png_gamma_shift[shift]) >> 4);

                for (j = 0; j < 256; j++)
                {
                    png_ptr->gamma_16_table[i][j] =
                        (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /
                                          65535.0, g) * 65535.0 + .5);
                }
            }
        }

        #if defined (PNG_READ_BACKGROUND_SUPPORTED) || \
        defined (PNG_READ_RGB_TO_GRAY_SUPPORTED)
        if (png_ptr->transformations & (PNG_BACKGROUND | PNG_RGB_TO_GRAY))
        {

            g = 1.0 / (png_ptr->gamma);

            png_ptr->gamma_16_to_1 = (png_uint_16pp)png_calloc(png_ptr,
                                                               (png_uint_32)(num * png_sizeof(png_uint_16p)));

            for (i = 0; i < num; i++)
            {
                png_ptr->gamma_16_to_1[i] = (png_uint_16p)png_malloc(png_ptr,
                                                                     (png_uint_32)(256 * png_sizeof(png_uint_16)));

                ig = (((png_uint_32)i *
                       (png_uint_32)png_gamma_shift[shift]) >> 4);
                for (j = 0; j < 256; j++)
                {
                    png_ptr->gamma_16_to_1[i][j] =
                        (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /
                                          65535.0, g) * 65535.0 + .5);
                }
            }

            if (png_ptr->screen_gamma > 0.000001)
                g = 1.0 / png_ptr->screen_gamma;

            else
                g = png_ptr->gamma; /* Probably doing rgb_to_gray */

            png_ptr->gamma_16_from_1 = (png_uint_16pp)png_calloc(png_ptr,
                                                                 (png_uint_32)(num * png_sizeof(png_uint_16p)));

            for (i = 0; i < num; i++)
            {
                png_ptr->gamma_16_from_1[i] = (png_uint_16p)png_malloc(png_ptr,
                                                                       (png_uint_32)(256 * png_sizeof(png_uint_16)));

                ig = (((png_uint_32)i *
                       (png_uint_32)png_gamma_shift[shift]) >> 4);

                for (j = 0; j < 256; j++)
                {
                    png_ptr->gamma_16_from_1[i][j] =
                        (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /
                                          65535.0, g) * 65535.0 + .5);
                }
            }
        }
        #endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_RGB_TO_GRAY_SUPPORTED */
    }
}
        #endif
/* To do: install integer version of png_build_gamma_table here */
    #endif

    #ifdef PNG_MNG_FEATURES_SUPPORTED
/* Undoes intrapixel differencing  */
void /* PRIVATE */
png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
{
    png_debug(1, "in png_do_read_intrapixel");

    if (
        (row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
        int bytes_per_pixel;
        png_uint_32 row_width = row_info->width;
        if (row_info->bit_depth == 8)
        {
            png_bytep rp;
            png_uint_32 i;

            if (row_info->color_type == PNG_COLOR_TYPE_RGB)
                bytes_per_pixel = 3;

            else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
                bytes_per_pixel = 4;

            else
                return;

            for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
            {
                *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
                *(rp + 2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
            }
        }
        else if (row_info->bit_depth == 16)
        {
            png_bytep rp;
            png_uint_32 i;

            if (row_info->color_type == PNG_COLOR_TYPE_RGB)
                bytes_per_pixel = 6;

            else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
                bytes_per_pixel = 8;

            else
                return;

            for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
            {
                png_uint_32 s0 = (*(rp) << 8) | *(rp + 1);
                png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
                png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
                png_uint_32 red = (png_uint_32)((s0 + s1 + 65536L) & 0xffffL);
                png_uint_32 blue = (png_uint_32)((s2 + s1 + 65536L) & 0xffffL);
                *(rp) = (png_byte)((red >> 8) & 0xff);
                *(rp + 1) = (png_byte)(red & 0xff);
                *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
                *(rp + 5) = (png_byte)(blue & 0xff);
            }
        }
    }
}
    #endif /* PNG_MNG_FEATURES_SUPPORTED */
#endif /* PNG_READ_SUPPORTED */